diff --git a/Cantera/python/src/ctonedim_methods.cpp b/Cantera/python/src/ctonedim_methods.cpp
index f797dd3b4..29e29d5a3 100644
--- a/Cantera/python/src/ctonedim_methods.cpp
+++ b/Cantera/python/src/ctonedim_methods.cpp
@@ -619,7 +619,7 @@ py_sim1D_new(PyObject *self, PyObject *args)
     size_t domains_len = domains_array->dimensions[0];
 
     int * domains_data = (int *) malloc(sizeof(int) * domains_len);
-    for (int i = 0; i <  domains_len; i++) {
+    for (size_t i = 0; i <  domains_len; i++) {
       domains_data[i] = (int) dd_data[i];
     }
  
diff --git a/Cantera/src/base/xml.cpp b/Cantera/src/base/xml.cpp
index 7c83f6e2d..e1141ecd2 100644
--- a/Cantera/src/base/xml.cpp
+++ b/Cantera/src/base/xml.cpp
@@ -514,7 +514,7 @@ namespace Cantera {
    */
   XML_Node& XML_Node::addChild(XML_Node& node) {
     m_children.push_back(&node);
-    m_nchildren = static_cast<int>(m_children.size());
+    m_nchildren = m_children.size();
     m_childindex[node.name()] = m_children.back();
     node.setRoot(root());
     node.setParent(this);
@@ -533,7 +533,7 @@ namespace Cantera {
   XML_Node& XML_Node::addChild(const std::string &sname) { 
     XML_Node *xxx = new XML_Node(sname, this);
     m_children.push_back(xxx);
-    m_nchildren = static_cast<int>(m_children.size());
+    m_nchildren = m_children.size();
     m_childindex[sname] = m_children.back();
     xxx->setRoot(root());
     xxx->setParent(this);
@@ -589,7 +589,7 @@ namespace Cantera {
     vector<XML_Node*>::iterator i;
     i = find(m_children.begin(), m_children.end(), node);
     m_children.erase(i);
-    m_nchildren = static_cast<int>(m_children.size());
+    m_nchildren = m_children.size();
     m_childindex.erase(node->name());
   }
 
@@ -824,7 +824,7 @@ namespace Cantera {
   /*
    *
    */
-  int XML_Node::nChildren() const { 
+  size_t XML_Node::nChildren() const {
     return m_nchildren;
   }
  
@@ -873,13 +873,12 @@ namespace Cantera {
     XML_Node *scResult = 0;
     XML_Node *sc;
     std::string idattrib = id();
-    int n;
     if (name() == nameTarget) {
       if (idTarget == "" || idTarget == idattrib) {
 	return const_cast<XML_Node*>(this);
       }
     }
-    for (n = 0; n < m_nchildren; n++) {
+    for (size_t n = 0; n < m_nchildren; n++) {
       sc = m_children[n];
       if (sc->name() == nameTarget) {
 	if (idTarget == "") return sc;
@@ -887,7 +886,7 @@ namespace Cantera {
 	if (idTarget == idattrib) return sc;
       }
     }
-    for (n = 0; n < m_nchildren; n++) {
+    for (size_t n = 0; n < m_nchildren; n++) {
       sc = m_children[n];
       scResult = sc->findNameID(nameTarget, idTarget);
       if (scResult) return scResult;
@@ -1094,7 +1093,7 @@ namespace Cantera {
       }
     }
     const vector<XML_Node*> &vsc = node_dest->children();
-    for (int n = 0; n < m_nchildren; n++) {
+    for (size_t n = 0; n < m_nchildren; n++) {
       sc = m_children[n];
       ndc = node_dest->nChildren();
       dc = 0;
@@ -1147,7 +1146,7 @@ namespace Cantera {
     }
     const vector<XML_Node*> &vsc = node_dest->children();
 
-    for (int n = 0; n < m_nchildren; n++) {
+    for (size_t n = 0; n < m_nchildren; n++) {
       sc = m_children[n];
       ndc = node_dest->nChildren();
       (void) node_dest->addChild(sc->name());
@@ -1159,7 +1158,7 @@ namespace Cantera {
   // Set the lock for this node
   void XML_Node::lock() {
     m_locked = true;
-    for (int i = 0; i < m_nchildren; i++) {
+    for (size_t i = 0; i < m_nchildren; i++) {
       m_children[i]->lock();
     }
   }
@@ -1167,7 +1166,7 @@ namespace Cantera {
   // Unset the lock for this node
   void XML_Node::unlock() {
     m_locked = false;
-    for (int i = 0; i < m_nchildren; i++) {
+    for (size_t i = 0; i < m_nchildren; i++) {
       m_children[i]->unlock();
     }
   }
@@ -1336,8 +1335,7 @@ namespace Cantera {
 	  }
 	}
       }
-      int i;
-      for (i = 0; i < m_nchildren; i++) {
+      for (size_t i = 0; i < m_nchildren; i++) {
 	s << endl;
 	m_children[i]->write_int(s,level + 2);
       }
@@ -1358,7 +1356,7 @@ namespace Cantera {
    */
   void XML_Node::write(std::ostream& s, const int level) const {
     if (m_name == "--" && m_root == this) {
-      for (int i = 0; i < m_nchildren; i++) {
+      for (size_t i = 0; i < m_nchildren; i++) {
 	m_children[i]->write_int(s,level);
 	s << endl;
       }
@@ -1391,8 +1389,7 @@ namespace Cantera {
     }
 
     const vector<XML_Node*> &vsc = root->children();
-    int n;
-    for (n = 0; n < root->nChildren(); n++) {
+    for (size_t n = 0; n < root->nChildren(); n++) {
       sc = vsc[n];
       if (sc->name() == "phase") {
 	if (idtarget == "") return sc;
@@ -1400,7 +1397,7 @@ namespace Cantera {
 	if (idtarget == idattrib) return sc;
       }
     }
-    for (n = 0; n < root->nChildren(); n++) {
+    for (size_t n = 0; n < root->nChildren(); n++) {
       sc = vsc[n];
       if  (sc->name() != "phase") {
 	scResult = findXMLPhase(sc, idtarget);
diff --git a/Cantera/src/base/xml.h b/Cantera/src/base/xml.h
index 5112927a2..66b87c6b2 100644
--- a/Cantera/src/base/xml.h
+++ b/Cantera/src/base/xml.h
@@ -470,7 +470,7 @@ namespace Cantera {
     /*!
      *
      */
-    int nChildren() const;
+    size_t nChildren() const;
 
     //!    Require that the current xml node have an attribute named
     //!    by the first argument, a, and that this attribute have the
@@ -746,7 +746,7 @@ namespace Cantera {
     std::vector<XML_Node*> m_children;
 
     //! Number of children of this node
-    int m_nchildren;
+    size_t m_nchildren;
 
     //! True if the current node is a comment node
     bool m_iscomment;
diff --git a/Cantera/src/converters/CKParser.cpp b/Cantera/src/converters/CKParser.cpp
index aa0771ada..96b5dc374 100755
--- a/Cantera/src/converters/CKParser.cpp
+++ b/Cantera/src/converters/CKParser.cpp
@@ -648,7 +648,7 @@ next:
 		log << endl << " Default # of temperature regions: " 
 		    << nreg << endl;
 		log << "          ";
-		for (int i = 0; i <= nreg; i++) {
+		for (size_t i = 0; i <= nreg; i++) {
 		  log << temp[i] << "  ";
 		}
 		log << endl;
diff --git a/Cantera/src/converters/CKReader.cpp b/Cantera/src/converters/CKReader.cpp
index 397500aac..64f5c2eda 100755
--- a/Cantera/src/converters/CKReader.cpp
+++ b/Cantera/src/converters/CKReader.cpp
@@ -352,10 +352,9 @@ bool CKReader::writeReactions(std::ostream& log) {
 
 /// validate the species
 bool CKReader::validateSpecies(std::ostream& log) {
-    int nel = static_cast<int>(elements.size());
-    int nsp = static_cast<int>(species.size());
+    size_t nel = elements.size();
+    size_t nsp = species.size();
     double tol;
-    int j, k, m;
 
     log << newTask("validating species");
 
@@ -363,7 +362,7 @@ bool CKReader::validateSpecies(std::ostream& log) {
     vector<string> esyms;
 
     log << "   checking that all species have been defined... ";
-    for (k = 0; k < nsp; k++) {
+    for (size_t k = 0; k < nsp; k++) {
 	Species& s = species[k];
         if (s.valid == 0) {
             log << endl << "   species " << s.name << " undefined ";
@@ -377,14 +376,14 @@ bool CKReader::validateSpecies(std::ostream& log) {
     }
 
     log << "   checking that all species elements have been declared... ";
-    for (k = 0; k < nsp; k++) {
-
+    for (size_t k = 0; k < nsp; k++) {
 	Species& s = species[k];
 
 	getMapKeys(s.comp, esyms);
 	size_t nm = esyms.size();
 
-	for (m = 0; m < nm; m++) {
+	for (size_t m = 0; m < nm; m++) {
+	  size_t j;
 	  for (j = 0; j < nel; j++) {
 		if (esyms[m] == elements[j].name) break;
 	  }
diff --git a/Cantera/src/numerics/CVodeInt.cpp b/Cantera/src/numerics/CVodeInt.cpp
index 31291ef10..148f759e1 100644
--- a/Cantera/src/numerics/CVodeInt.cpp
+++ b/Cantera/src/numerics/CVodeInt.cpp
@@ -127,7 +127,7 @@ namespace Cantera {
       if (m_abstol) N_VFree(nv(m_abstol));
       m_abstol = reinterpret_cast<void*>(N_VNew(m_nabs, 0));
     }
-    for (int i=0; i<n; i++) {
+    for (int i=0; i<m_nabs; i++) {
       N_VIth(nv(m_abstol), i) = abstol[i];
     }
     m_reltol = reltol; 
diff --git a/Cantera/src/numerics/CVodesIntegrator.cpp b/Cantera/src/numerics/CVodesIntegrator.cpp
index 15c545188..6984a44de 100644
--- a/Cantera/src/numerics/CVodesIntegrator.cpp
+++ b/Cantera/src/numerics/CVodesIntegrator.cpp
@@ -270,7 +270,7 @@ namespace Cantera {
       N_VDestroy_Serial(nv(m_y));    // free solution vector if already allocated
     }
     m_y = reinterpret_cast<void*>(N_VNew_Serial(m_neq));   // allocate solution vector
-    for (int i=0; i<m_neq; i++) {
+    for (size_t i = 0; i < m_neq; i++) {
       NV_Ith_S(nv(m_y), i) = 0.0;
     }
     // check abs tolerance array size
diff --git a/Cantera/src/numerics/Func1.h b/Cantera/src/numerics/Func1.h
index 31cb07956..14aaee763 100644
--- a/Cantera/src/numerics/Func1.h
+++ b/Cantera/src/numerics/Func1.h
@@ -824,7 +824,7 @@ namespace Cantera {
    */
   class Poly1 : public Func1 {
   public:
-    Poly1(int n, doublereal* c) :
+    Poly1(size_t n, doublereal* c) :
       Func1()
     {
       m_n = n+1;
@@ -857,9 +857,8 @@ namespace Cantera {
     }
 
     virtual doublereal eval(doublereal t) const {
-      int n;
       doublereal r = m_cpoly[m_n-1];
-      for (n = 1; n < m_n; n++) {
+      for (size_t n = 1; n < m_n; n++) {
 	r *= t;
 	r += m_cpoly[m_n - n - 1];
       }
@@ -867,7 +866,7 @@ namespace Cantera {
     }
 
   protected:
-    int m_n;
+    size_t m_n;
     vector_fp m_cpoly;
   };
 
@@ -882,7 +881,7 @@ namespace Cantera {
    */
   class Fourier1 : public Func1 {
   public:
-    Fourier1(int n, doublereal omega, doublereal a0,
+    Fourier1(size_t n, doublereal omega, doublereal a0,
 	     doublereal* a, doublereal* b) :
       Func1()
     {
@@ -921,7 +920,7 @@ namespace Cantera {
     }
 
     virtual doublereal eval(doublereal t) const {
-      int n, nn;
+      size_t n, nn;
       doublereal sum = m_a0_2;
       for (n = 0; n < m_n; n++) {
 	nn = n + 1;
@@ -932,7 +931,7 @@ namespace Cantera {
     }
 
   protected:
-    int m_n;
+    size_t m_n;
     doublereal m_omega, m_a0_2;
     vector_fp m_ccos, m_csin;
   };
@@ -946,16 +945,15 @@ namespace Cantera {
    */
   class Arrhenius1 : public Func1 {
   public:
-    Arrhenius1(int n, doublereal* c) :
+    Arrhenius1(size_t n, doublereal* c) :
       Func1()
     {
       m_n = n;
       m_A.resize(n);
       m_b.resize(n);
       m_E.resize(n);
-      int loc;
-      for (int i = 0; i < n; i++) {
-	loc = 3*i;
+      for (size_t i = 0; i < n; i++) {
+	size_t loc = 3*i;
 	m_A[i] = c[loc];
 	m_b[i] = c[loc+1];
 	m_E[i] = c[loc+2];
@@ -988,16 +986,15 @@ namespace Cantera {
     }
 
     virtual doublereal eval(doublereal t) const {
-      int n;
       doublereal sum = 0.0;
-      for (n = 0; n < m_n; n++) {
+      for (size_t n = 0; n < m_n; n++) {
 	sum += m_A[n]*std::pow(t,m_b[n])*std::exp(-m_E[n]/t);
       }
       return sum;
     }
 
   protected:
-    int m_n;
+    size_t m_n;
     vector_fp m_A, m_b, m_E;
   };
 
diff --git a/apps/bvp/AxiStagnBVP.cpp b/apps/bvp/AxiStagnBVP.cpp
index c2739d8fb..46adcf7cd 100644
--- a/apps/bvp/AxiStagnBVP.cpp
+++ b/apps/bvp/AxiStagnBVP.cpp
@@ -94,7 +94,7 @@ void StFlow::setGasAtMidpoint(const doublereal* x,int j) {
     m_thermo->setTemperature(0.5*(T(x,j)+T(x,j+1)));
     const doublereal* yyj = x + m_nv*j + 4;
     const doublereal* yyjp = x + m_nv*(j+1) + 4;
-    for (int k = 0; k < m_nsp; k++)
+    for (size_t k = 0; k < m_nsp; k++)
         m_ybar[k] = 0.5*(yyj[k] + yyjp[k]);
     m_thermo->setMassFractions_NoNorm(DATA_PTR(m_ybar));
     m_thermo->setPressure(m_press);
diff --git a/apps/bvp/stagnation.cpp b/apps/bvp/stagnation.cpp
index 983906224..003d9d624 100644
--- a/apps/bvp/stagnation.cpp
+++ b/apps/bvp/stagnation.cpp
@@ -116,7 +116,7 @@ AxiStagnBVP::AxiStagnBVP(igthermo_t* ph, int nsp, int points) :
         m_refiner->setActive(3, false);
 
         vector_fp gr;
-        for (int ng = 0; ng < m_points; ng++) gr.push_back(1.0*ng/m_points);
+        for (size_t ng = 0; ng < m_points; ng++) gr.push_back(1.0*ng/m_points);
         setupGrid(m_points, DATA_PTR(gr));
         setID("stagnation flow");
     }
@@ -221,7 +221,7 @@ AxiStagnBVP::AxiStagnBVP(igthermo_t* ph, int nsp, int points) :
         m_thermo->setTemperature(0.5*(T(x,j)+T(x,j+1)));
         const doublereal* yyj = x + m_nv*j + c_offset_Y;
         const doublereal* yyjp = x + m_nv*(j+1) + c_offset_Y;
-        for (int k = 0; k < m_nsp; k++)
+        for (size_t k = 0; k < m_nsp; k++)
             m_ybar[k] = 0.5*(yyj[k] + yyjp[k]);
         m_thermo->setMassFractions_NoNorm(DATA_PTR(m_ybar));
         m_thermo->setPressure(m_press);