diff --git a/src/base/application.cpp b/src/base/application.cpp
index c6c60c7ce..8ede85fef 100644
--- a/src/base/application.cpp
+++ b/src/base/application.cpp
@@ -366,7 +366,7 @@ long int Application::readStringRegistryKey(const std::string& keyName, const st
 
 void Application::Messages::popError()
 {
-    if (static_cast<int>(errorMessage.size()) > 0) {
+    if (!errorMessage.empty()) {
         errorRoutine.pop_back() ;
         errorMessage.pop_back() ;
     }
@@ -374,7 +374,7 @@ void Application::Messages::popError()
 
 std::string Application::Messages::lastErrorMessage()
 {
-    if (static_cast<int>(errorMessage.size()) > 0) {
+    if (!errorMessage.empty()) {
         string head =
             "\n\n************************************************\n"
             "                Cantera Error!                  \n"
@@ -388,7 +388,7 @@ std::string Application::Messages::lastErrorMessage()
 
 void Application::Messages::getErrors(std::ostream& f)
 {
-    int i = static_cast<int>(errorMessage.size());
+    size_t i = errorMessage.size();
     if (i == 0) {
         return;
     }
@@ -397,8 +397,7 @@ void Application::Messages::getErrors(std::ostream& f)
     f << "                   Cantera Error!                  " << endl;
     f << "************************************************" << endl
       << endl;
-    int j;
-    for (j = 0; j < i; j++) {
+    for (size_t j = 0; j < i; j++) {
         f << endl;
         f << "Procedure: " << errorRoutine[j] << endl;
         f << "Error:     " << errorMessage[j] << endl;
@@ -410,7 +409,7 @@ void Application::Messages::getErrors(std::ostream& f)
 
 void Application::Messages::logErrors()
 {
-    int i = static_cast<int>(errorMessage.size());
+    size_t i = errorMessage.size();
     if (i == 0) {
         return;
     }
@@ -418,8 +417,7 @@ void Application::Messages::logErrors()
     writelog("************************************************\n");
     writelog("                   Cantera Error!                  \n");
     writelog("************************************************\n\n");
-    int j;
-    for (j = 0; j < i; j++) {
+    for (size_t j = 0; j < i; j++) {
         writelog("\n");
         writelog(string("Procedure: ")+ errorRoutine[j]+" \n");
         writelog(string("Error:     ")+ errorMessage[j]+" \n");
@@ -516,12 +514,10 @@ std::string Application::findInputFile(const std::string& name)
     string inname;
     std::vector<string>& dirs = inputDirs;
 
-    int nd;
     if (islash == string::npos && ibslash == string::npos) {
-        nd = static_cast<int>(dirs.size());
-        int i;
+        size_t nd = dirs.size();
         inname = "";
-        for (i = 0; i < nd; i++) {
+        for (size_t i = 0; i < nd; i++) {
             inname = dirs[i] + "/" + name;
             std::ifstream fin(inname.c_str());
             if (fin) {
@@ -533,9 +529,9 @@ std::string Application::findInputFile(const std::string& name)
         msg = "\nInput file " + name
               + " not found in director";
         msg += (nd == 1 ? "y " : "ies ");
-        for (i = 0; i < nd; i++) {
+        for (size_t i = 0; i < nd; i++) {
             msg += "\n'" + dirs[i] + "'";
-            if (i < nd-1) {
+            if (i+1 < nd) {
                 msg += ", ";
             }
         }
diff --git a/src/base/ctml.cpp b/src/base/ctml.cpp
index 8406349fc..fc988f8e2 100644
--- a/src/base/ctml.cpp
+++ b/src/base/ctml.cpp
@@ -209,10 +209,9 @@ void getIntegers(const Cantera::XML_Node& node,
 {
     std::vector<XML_Node*> f;
     node.getChildren("integer",f);
-    int n = static_cast<int>(f.size());
     integer x;
     std::string typ, title, vmin, vmax;
-    for (int i = 0; i < n; i++) {
+    for (size_t i = 0; i < f.size(); i++) {
         const XML_Node& fi = *(f[i]);
         x = atoi(fi().c_str());
         title = fi["title"];
@@ -232,10 +231,9 @@ void getFloats(const Cantera::XML_Node& node, std::map<std::string, double>& v,
                     "To be removed in Cantera 2.2.");
     std::vector<XML_Node*> f;
     node.getChildren("float",f);
-    int n = static_cast<int>(f.size());
     doublereal x, x0, x1, fctr;
     std::string typ, title, units, vmin, vmax;
-    for (int i = 0; i < n; i++) {
+    for (size_t i = 0; i < f.size(); i++) {
         const XML_Node& fi = *(f[i]);
         x = fpValue(fi());
         x0 = Undef;
@@ -510,9 +508,8 @@ void getMap(const Cantera::XML_Node& node, std::map<std::string, std::string>& m
     std::vector<std::string> v;
     getStringArray(node, v);
     std::string key, val;
-    int n = static_cast<int>(v.size());
     string::size_type icolon;
-    for (int i = 0; i < n; i++) {
+    for (size_t i = 0; i < v.size(); i++) {
         icolon = v[i].find(":");
         if (icolon == string::npos) {
             throw CanteraError("getMap","missing colon in map entry ("
diff --git a/src/base/plots.cpp b/src/base/plots.cpp
index 3fe978f4a..bf17c7955 100644
--- a/src/base/plots.cpp
+++ b/src/base/plots.cpp
@@ -36,23 +36,20 @@ void outputTEC(std::ostream& s, const std::string& title,
                const std::vector<std::string>& names,
                const Array2D& data)
 {
-    int i,j;
-    int npts = static_cast<int>(data.nColumns());
-    int nv = static_cast<int>(data.nRows());
     s << "TITLE     = \"" + title + "\"" << endl;
     s << "VARIABLES = " << endl;
-    for (i = 0; i < nv; i++) {
+    for (size_t i = 0; i < data.nRows(); i++) {
         s << "\"" << names[i] << "\"" << endl;
     }
     s << "ZONE T=\"zone1\"" << endl;
-    s << " I=" << npts << ",J=1,K=1,F=POINT" << endl;
+    s << " I=" << data.nColumns() << ",J=1,K=1,F=POINT" << endl;
     s << "DT=( ";
-    for (i = 0; i < nv; i++) {
+    for (size_t i = 0; i < data.nRows(); i++) {
         s << " SINGLE";
     }
     s << " )" << endl;
-    for (i = 0; i < npts; i++) {
-        for (j = 0; j < nv; j++) {
+    for (size_t i = 0; i < data.nColumns(); i++) {
+        for (size_t j = 0; j < data.nRows(); j++) {
             s << data(j,i) << " ";
         }
         s << endl;
@@ -63,21 +60,18 @@ void outputExcel(std::ostream& s, const std::string& title,
                  const std::vector<std::string>& names,
                  const Array2D& data)
 {
-    int i,j;
-    int npts = static_cast<int>(data.nColumns());
-    int nv = static_cast<int>(data.nRows());
     s << title + "," << endl;
-    for (i = 0; i < nv; i++) {
+    for (size_t i = 0; i < data.nRows(); i++) {
         s << names[i];
-        if (i != nv-1) {
+        if (i != data.nRows()-1) {
             s << ",";
         }
     }
     s << endl;
-    for (i = 0; i < npts; i++) {
-        for (j = 0; j < nv; j++) {
+    for (size_t i = 0; i < data.nColumns(); i++) {
+        for (size_t j = 0; j < data.nRows(); j++) {
             s << data(j,i);
-            if (j != nv-1) {
+            if (j != data.nRows()-1) {
                 s << ",";
             }
         }
diff --git a/src/base/stringUtils.cpp b/src/base/stringUtils.cpp
index 21622f4f8..ab4e92349 100644
--- a/src/base/stringUtils.cpp
+++ b/src/base/stringUtils.cpp
@@ -57,9 +57,8 @@ std::string int2str(const size_t n)
 
 std::string lowercase(const std::string& s)
 {
-    int n = static_cast<int>(s.size());
     std::string lc(s);
-    for (int i = 0; i < n; i++) {
+    for (size_t i = 0; i < s.size(); i++) {
         lc[i] = (char) tolower(s[i]);
     }
     return lc;
@@ -109,10 +108,8 @@ std::string stripws(const std::string& s)
 
 std::string stripnonprint(const std::string& s)
 {
-    int i;
-    int n = static_cast<int>(s.size());
     std::string ss = "";
-    for (i = 0; i < n; i++) {
+    for (size_t i = 0; i < s.size(); i++) {
         if (isprint(s[i])) {
             ss += s[i];
         }
diff --git a/src/base/units.h b/src/base/units.h
index b8d1e7aca..482a988cc 100644
--- a/src/base/units.h
+++ b/src/base/units.h
@@ -77,7 +77,6 @@ public:
         }
 
         doublereal f = 1.0, fctr;
-        int tsize;
         std::string u = units_, tok, tsub;
         std::string::size_type k;
         char action = '-';
@@ -92,7 +91,7 @@ public:
             } else {
                 tok = u;
             }
-            tsize = static_cast<int>(tok.size());
+            size_t tsize = tok.size();
             if (tsize == 0) {
                 fctr = 1.0;
             } else if (tok[tsize - 1] == '2') {
diff --git a/src/base/xml.cpp b/src/base/xml.cpp
index e14d06cae..b6839f039 100644
--- a/src/base/xml.cpp
+++ b/src/base/xml.cpp
@@ -343,8 +343,7 @@ XML_Node::XML_Node(const XML_Node& right) :
 XML_Node& XML_Node::operator=(const XML_Node& right)
 {
     if (&right != this) {
-        int n = static_cast<int>(m_children.size());
-        for (int i = 0; i < n; i++) {
+        for (size_t i = 0; i < m_children.size(); i++) {
             if (m_children[i]) {
                 if (m_children[i]->parent() == this) {
                     delete m_children[i];
@@ -363,8 +362,7 @@ XML_Node::~XML_Node()
     if (m_locked) {
         writelog("XML_Node::~XML_Node: deleted a locked XML_Node: "+name());
     }
-    int n = static_cast<int>(m_children.size());
-    for (int i = 0; i < n; i++) {
+    for (size_t i = 0; i < m_children.size(); i++) {
         if (m_children[i]) {
             if (m_children[i]->parent() == this) {
                 delete m_children[i];
@@ -376,8 +374,7 @@ XML_Node::~XML_Node()
 
 void XML_Node::clear()
 {
-    int n = static_cast<int>(m_children.size());
-    for (int i = 0; i < n; i++) {
+    for (size_t i = 0; i < m_children.size(); i++) {
         if (m_children[i]) {
             if (m_children[i]->parent() == this) {
                 delete m_children[i];
@@ -948,8 +945,7 @@ void XML_Node::write_int(std::ostream& s, int level, int numRecursivesAllowed) c
             s << " ";
         }
         s << m_value;
-        int ll = static_cast<int>(m_value.size()) - 1;
-        if (! isspace(m_value[ll])) {
+        if (! isspace(m_value[m_value.size()-1])) {
             s << " ";
         }
         s << "-->";
@@ -987,10 +983,10 @@ void XML_Node::write_int(std::ostream& s, int level, int numRecursivesAllowed) c
                         }
                         vv = vv.substr(ieol+1);
                     } else {
-                        int lll = static_cast<int>(vv.size()) - 1;
-                        if (lll >= 0) {
-                            int jf = lll;
-                            for (int j = 0; j < lll; j++) {
+                        size_t lll = vv.size() - 1;
+                        if (lll != npos) {
+                            size_t jf = lll;
+                            for (size_t j = 0; j < lll; j++) {
                                 if (! isspace(vv[j])) {
                                     jf = j;
                                     break;
@@ -1007,7 +1003,7 @@ void XML_Node::write_int(std::ostream& s, int level, int numRecursivesAllowed) c
             } else {
                 bool doSpace = true;
                 bool doNewLine = false;
-                int ll = static_cast<int>(m_value.size()) - 1;
+                size_t ll = m_value.size() - 1;
                 if (ll > 25) {
                     doNewLine = true;
                 }
diff --git a/src/clib/Cabinet.h b/src/clib/Cabinet.h
index 5618af6a1..c75db311f 100644
--- a/src/clib/Cabinet.h
+++ b/src/clib/Cabinet.h
@@ -118,8 +118,7 @@ public:
      */
     static int clear() {
         dataRef data = getData();
-        int n = static_cast<int>(data.size());
-        for (int i = 1; i < n; i++) {
+        for (size_t i = 1; i < data.size(); i++) {
             del(i);
         }
         if (canDelete) {
diff --git a/src/kinetics/importKinetics.cpp b/src/kinetics/importKinetics.cpp
index c67eb0c4e..f6bb14f78 100644
--- a/src/kinetics/importKinetics.cpp
+++ b/src/kinetics/importKinetics.cpp
@@ -402,8 +402,8 @@ static void getFalloff(const XML_Node& f, ReactionData& rdata)
     vector<string> p;
     getStringArray(f,p);
     vector_fp c;
-    int np = static_cast<int>(p.size());
-    for (int n = 0; n < np; n++) {
+    size_t np = p.size();
+    for (size_t n = 0; n < np; n++) {
         c.push_back(fpValue(p[n]));
     }
     if (type == "Troe") {
@@ -825,12 +825,11 @@ bool installReactionArrays(const XML_Node& p, Kinetics& kin,
      * end result being purely additive.
      */
     p.getChildren("reactionArray",rarrays);
-    int na = static_cast<int>(rarrays.size());
-    if (na == 0) {
+    if (rarrays.empty()) {
         kin.finalize();
         return false;
     }
-    for (int n = 0; n < na; n++) {
+    for (size_t n = 0; n < rarrays.size(); n++) {
         /*
          * Go get a reference to the current xml element,
          * reactionArray. We will process this element now.
@@ -868,7 +867,6 @@ bool installReactionArrays(const XML_Node& p, Kinetics& kin,
                 rxnrule.skipUndeclaredThirdBodies = true;
             }
         }
-        int i, nrxns = 0;
         /*
          * Search for child elements called include. We only include
          * a reaction if it's tagged by one of the include fields.
@@ -876,14 +874,12 @@ bool installReactionArrays(const XML_Node& p, Kinetics& kin,
          */
         vector<XML_Node*> incl;
         rxns.getChildren("include",incl);
-        int ninc = static_cast<int>(incl.size());
 
         vector<XML_Node*> allrxns;
         rdata->getChildren("reaction",allrxns);
-        nrxns = static_cast<int>(allrxns.size());
         // if no 'include' directive, then include all reactions
-        if (ninc == 0) {
-            for (i = 0; i < nrxns; i++) {
+        if (incl.empty()) {
+            for (size_t i = 0; i < allrxns.size(); i++) {
                 const XML_Node* r = allrxns[i];
                 if (r) {
                     if (_rxns.installReaction(itot, *r, kin,
@@ -893,7 +889,7 @@ bool installReactionArrays(const XML_Node& p, Kinetics& kin,
                 }
             }
         } else {
-            for (int nii = 0; nii < ninc; nii++) {
+            for (size_t nii = 0; nii < incl.size(); nii++) {
                 const XML_Node& ii = *incl[nii];
                 string imin = ii["min"];
                 string imax = ii["max"];
@@ -907,7 +903,7 @@ bool installReactionArrays(const XML_Node& p, Kinetics& kin,
                     }
                 }
 
-                for (i = 0; i < nrxns; i++) {
+                for (size_t i = 0; i < allrxns.size(); i++) {
                     const XML_Node* r = allrxns[i];
                     string rxid;
                     if (r) {
diff --git a/src/oneD/StFlow.cpp b/src/oneD/StFlow.cpp
index 624e440ee..6d9d3cb30 100644
--- a/src/oneD/StFlow.cpp
+++ b/src/oneD/StFlow.cpp
@@ -598,8 +598,7 @@ void StFlow::restore(const XML_Node& dom, doublereal* soln, int loglevel)
 
     vector<XML_Node*> str;
     dom.getChildren("string",str);
-    int nstr = static_cast<int>(str.size());
-    for (int istr = 0; istr < nstr; istr++) {
+    for (size_t istr = 0; istr < str.size(); istr++) {
         const XML_Node& nd = *str[istr];
         writelog(nd["title"]+": "+nd.value()+"\n");
     }
diff --git a/src/thermo/DebyeHuckel.cpp b/src/thermo/DebyeHuckel.cpp
index a133e7ccb..8f862b455 100644
--- a/src/thermo/DebyeHuckel.cpp
+++ b/src/thermo/DebyeHuckel.cpp
@@ -705,8 +705,7 @@ initThermoXML(XML_Node& phaseNode, const std::string& id_)
         XML_Node& scNode = thermoNode.child("solvent");
         vector<std::string> nameSolventa;
         getStringArray(scNode, nameSolventa);
-        int nsp = static_cast<int>(nameSolventa.size());
-        if (nsp != 1) {
+        if (nameSolventa.size() != 1) {
             throw CanteraError("DebyeHuckel::initThermoXML",
                                "badly formed solvent XML node");
         }
diff --git a/src/thermo/HMWSoln_input.cpp b/src/thermo/HMWSoln_input.cpp
index 72f9388e2..994852351 100644
--- a/src/thermo/HMWSoln_input.cpp
+++ b/src/thermo/HMWSoln_input.cpp
@@ -1058,8 +1058,7 @@ void HMWSoln::constructPhaseXML(XML_Node& phaseNode, std::string id_)
         XML_Node& scNode = thermoNode.child("solvent");
         vector<string> nameSolventa;
         getStringArray(scNode, nameSolventa);
-        int nsp = static_cast<int>(nameSolventa.size());
-        if (nsp != 1) {
+        if (nameSolventa.size() != 1) {
             throw CanteraError("HMWSoln::constructPhaseXML",
                                "badly formed solvent XML node");
         }
@@ -1243,8 +1242,7 @@ initThermoXML(XML_Node& phaseNode, const std::string& id_)
         XML_Node& scNode = thermoNode.child("solvent");
         vector<string> nameSolventa;
         getStringArray(scNode, nameSolventa);
-        int nsp = static_cast<int>(nameSolventa.size());
-        if (nsp != 1) {
+        if (nameSolventa.size() != 1) {
             throw CanteraError("HMWSoln::initThermoXML",
                                "badly formed solvent XML node");
         }
diff --git a/src/thermo/IdealMolalSoln.cpp b/src/thermo/IdealMolalSoln.cpp
index dfadb865d..715fb25a8 100644
--- a/src/thermo/IdealMolalSoln.cpp
+++ b/src/thermo/IdealMolalSoln.cpp
@@ -561,8 +561,7 @@ void IdealMolalSoln::initThermoXML(XML_Node& phaseNode, const std::string& id_)
         XML_Node& scNode = thermoNode.child("solvent");
         std::vector<std::string> nameSolventa;
         getStringArray(scNode, nameSolventa);
-        int nsp = static_cast<int>(nameSolventa.size());
-        if (nsp != 1) {
+        if (nameSolventa.size() != 1) {
             throw CanteraError("IdealMolalSoln::initThermoXML",
                                "badly formed solvent XML node");
         }
diff --git a/src/thermo/Phase.cpp b/src/thermo/Phase.cpp
index 52c4dc3dc..ae77b5dbc 100644
--- a/src/thermo/Phase.cpp
+++ b/src/thermo/Phase.cpp
@@ -763,12 +763,8 @@ void Phase::addElementsFromXML(const XML_Node& phase)
         }
     }
 
-    int nel = static_cast<int>(enames.size());
-    int i;
-    string enm;
-    XML_Node* e = 0;
-    for (i = 0; i < nel; i++) {
-        e = 0;
+    for (size_t i = 0; i < enames.size(); i++) {
+        XML_Node* e = 0;
         if (local_db) {
             //writelog("looking in local database.");
             e = local_db->findByAttr("name",enames[i]);
diff --git a/src/thermo/SpeciesThermoFactory.cpp b/src/thermo/SpeciesThermoFactory.cpp
index 69788b56d..cc7788104 100644
--- a/src/thermo/SpeciesThermoFactory.cpp
+++ b/src/thermo/SpeciesThermoFactory.cpp
@@ -676,15 +676,13 @@ void SpeciesThermoFactory::installThermoForSpecies
     // These shouldn't interfere with the algorithm at any point.
     const std::vector<XML_Node*>& tpWC = thermo.children();
     std::vector<XML_Node*> tp;
-    for (int i = 0; i < static_cast<int>(tpWC.size()); i++) {
+    for (size_t i = 0; i < tpWC.size(); i++) {
         if (!(tpWC[i])->isComment()) {
             tp.push_back(tpWC[i]);
         }
     }
-    int nc = static_cast<int>(tp.size());
-    string mname = thermo["model"];
 
-    if (mname == "MineralEQ3") {
+    if (thermo["model"] == "MineralEQ3") {
         const XML_Node* f = tp[0];
         if (f->name() != "MinEQ3") {
             throw CanteraError("SpeciesThermoFactory::installThermoForSpecies",
@@ -692,7 +690,7 @@ void SpeciesThermoFactory::installThermoForSpecies
         }
         installMinEQ3asShomateThermoFromXML(speciesNode["name"], th_ptr, spthermo, k, f);
     } else {
-        if (nc == 1) {
+        if (tp.size() == 1) {
             const XML_Node* f = tp[0];
             if (f->name() == "Shomate") {
                 installShomateThermoFromXML(speciesNode["name"], spthermo, k, f, 0);
@@ -712,7 +710,7 @@ void SpeciesThermoFactory::installThermoForSpecies
                 throw UnknownSpeciesThermoModel("installThermoForSpecies",
                                                 speciesNode["name"], f->name());
             }
-        } else if (nc == 2) {
+        } else if (tp.size() == 2) {
             const XML_Node* f0 = tp[0];
             const XML_Node* f1 = tp[1];
             if (f0->name() == "NASA" && f1->name() == "NASA") {
@@ -727,7 +725,7 @@ void SpeciesThermoFactory::installThermoForSpecies
                 throw UnknownSpeciesThermoModel("installThermoForSpecies", speciesNode["name"],
                                                 f0->name() + " and " + f1->name());
             }
-        } else if (nc > 2) {
+        } else if (tp.size() > 2) {
             const XML_Node* f0 = tp[0];
             if (f0->name() == "NASA9") {
                 installNasa9ThermoFromXML(speciesNode["name"], spthermo, k, tp);
diff --git a/src/thermo/ThermoFactory.cpp b/src/thermo/ThermoFactory.cpp
index a252ab64a..0c86e8c99 100644
--- a/src/thermo/ThermoFactory.cpp
+++ b/src/thermo/ThermoFactory.cpp
@@ -476,9 +476,8 @@ bool importPhase(XML_Node& phase, ThermoPhase* th,
     XML_Node* db = 0;
     vector<XML_Node*> sparrays;
     phase.getChildren("speciesArray", sparrays);
-    int jsp, nspa = static_cast<int>(sparrays.size());
     if (ssConvention != cSS_CONVENTION_SLAVE) {
-        if (nspa == 0) {
+        if (sparrays.empty()) {
             throw CanteraError("importPhase",
                                "phase, " + th->id() + ", has zero \"speciesArray\" XML nodes.\n"
                                + " There must be at least one speciesArray nodes "
@@ -486,10 +485,10 @@ bool importPhase(XML_Node& phase, ThermoPhase* th,
         }
     }
     vector<XML_Node*> dbases;
-    vector_int sprule(nspa,0);
+    vector_int sprule(sparrays.size(),0);
 
     // loop over the speciesArray elements
-    for (jsp = 0; jsp < nspa; jsp++) {
+    for (size_t jsp = 0; jsp < sparrays.size(); jsp++) {
 
         const XML_Node& speciesArray = *sparrays[jsp];
 
diff --git a/src/zeroD/ReactorBase.cpp b/src/zeroD/ReactorBase.cpp
index 0187fb20a..47dc0f06b 100644
--- a/src/zeroD/ReactorBase.cpp
+++ b/src/zeroD/ReactorBase.cpp
@@ -86,9 +86,8 @@ void ReactorBase::setNetwork(ReactorNet* net)
 
 doublereal ReactorBase::residenceTime()
 {
-    int nout = static_cast<int>(m_outlet.size());
     doublereal mout = 0.0;
-    for (int i = 0; i < nout; i++) {
+    for (size_t i = 0; i < m_outlet.size(); i++) {
         mout += m_outlet[i]->massFlowRate();
     }
     return mass()/mout;