diff --git a/src/clib/Cabinet.h b/src/clib/Cabinet.h
index c75db311f..72bbc920a 100644
--- a/src/clib/Cabinet.h
+++ b/src/clib/Cabinet.h
@@ -134,7 +134,7 @@ public:
      * to it in the list is replaced by a pointer to the first element
      * in the list.
      */
-    static void del(int n) {
+    static void del(size_t n) {
         dataRef data = getData();
         if (n == 0) {
             return;
diff --git a/src/kinetics/importKinetics.cpp b/src/kinetics/importKinetics.cpp
index f6bb14f78..e748a3145 100644
--- a/src/kinetics/importKinetics.cpp
+++ b/src/kinetics/importKinetics.cpp
@@ -756,11 +756,11 @@ bool rxninfo::installReaction(int iRxn, const XML_Node& r, Kinetics& kin,
         unsigned long int participants = 0;
         for (size_t nn = 0; nn < rdata.reactants.size(); nn++) {
             rdata.net_stoich[-1 - int(rdata.reactants[nn])] -= rdata.rstoich[nn];
-            participants += rdata.reactants[nn];
+            participants += static_cast<unsigned long int>(rdata.reactants[nn]);
         }
         for (size_t nn = 0; nn < rdata.products.size(); nn++) {
             rdata.net_stoich[int(rdata.products[nn])+1] += rdata.pstoich[nn];
-            participants += 1000000 * rdata.products[nn];
+            participants += 1000000 * static_cast<unsigned long int>(rdata.products[nn]);
         }
 
         vector<size_t>& related = m_participants[participants];
diff --git a/src/thermo/NasaThermo.cpp b/src/thermo/NasaThermo.cpp
index 5a3d3e720..fffdacd2a 100644
--- a/src/thermo/NasaThermo.cpp
+++ b/src/thermo/NasaThermo.cpp
@@ -430,7 +430,7 @@ void NasaThermo::fixDiscontinuities(doublereal Tlow, doublereal Tmid,
     // First get the desired size of the work array
     ct_dgelss(nRows, nCols, 1, &M(0,0), nRows, &b[0], nRows,
               &sigma[0], -1, rank, &work[0], lwork, info);
-    work.resize(work[0]);
+    work.resize(static_cast<size_t>(work[0]));
     lwork = static_cast<int>(work[0]);
     ct_dgelss(nRows, nCols, 1, &M(0,0), nRows, &b[0], nRows,
               &sigma[0], -1, rank, &work[0], lwork, info);
diff --git a/src/transport/SolidTransport.cpp b/src/transport/SolidTransport.cpp
index 330a13c0c..4505a8890 100644
--- a/src/transport/SolidTransport.cpp
+++ b/src/transport/SolidTransport.cpp
@@ -142,9 +142,8 @@ doublereal SolidTransport::electricalConductivity()
         return m_electConductivity->getSpeciesTransProp();
     } else {
         getMobilities(&m_work[0]);
-        int nsp = m_thermo->nSpecies();
         doublereal sum = 0.0;
-        for (int k = 0; k < nsp; k++) {
+        for (size_t k = 0; k < m_thermo->nSpecies(); k++) {
             sum += m_thermo->charge(k) * m_thermo->moleFraction(k) * m_work[k];
         }
         return sum * m_thermo->molarDensity();
diff --git a/src/transport/TransportBase.cpp b/src/transport/TransportBase.cpp
index e616aea0e..5660d1c39 100644
--- a/src/transport/TransportBase.cpp
+++ b/src/transport/TransportBase.cpp
@@ -94,14 +94,14 @@ void Transport::setThermo(thermo_t& thermo)
         m_thermo = &thermo;
         m_nsp = m_thermo->nSpecies();
     } else  {
-        int newNum = thermo.nSpecies();
-        int oldNum = m_thermo->nSpecies();
+        size_t newNum = thermo.nSpecies();
+        size_t oldNum = m_thermo->nSpecies();
         if (newNum != oldNum) {
             throw CanteraError("Transport::setThermo",
                                "base object cannot be changed after "
                                "the transport manager has been constructed because num species isn't the same.");
         }
-        for (int i = 0; i < newNum; i++) {
+        for (size_t i = 0; i < newNum; i++) {
             std::string newS0 = thermo.speciesName(i);
             std::string oldS0 = m_thermo->speciesName(i);
             if (newNum != oldNum) {
diff --git a/src/transport/TransportFactory.cpp b/src/transport/TransportFactory.cpp
index 107e5420b..b632a7f2b 100644
--- a/src/transport/TransportFactory.cpp
+++ b/src/transport/TransportFactory.cpp
@@ -64,7 +64,7 @@ public:
      *  @param linenum  inputs the line number
      *  @param msg      String message to be sent to the user
      */
-    TransportDBError(int linenum, const std::string& msg) :
+    TransportDBError(size_t linenum, const std::string& msg) :
         CanteraError("getTransportData", "error reading transport data: "  + msg + "\n") {
     }
 };
@@ -580,7 +580,7 @@ void TransportFactory::setupSolidTransport(std::ostream& flog, thermo_t* thermo,
     // constant mixture attributes
     trParam.thermo = thermo;
     trParam.nsp_ = trParam.thermo->nSpecies();
-    int nsp = trParam.nsp_;
+    size_t nsp = trParam.nsp_;
 
     trParam.tmin = thermo->minTemp();
     trParam.tmax = thermo->maxTemp();
@@ -1118,8 +1118,8 @@ void TransportFactory::getSolidTransportData(const XML_Node& transportNode,
 {
     try {
 
-        int num = transportNode.nChildren();
-        for (int iChild = 0; iChild < num; iChild++) {
+        size_t num = transportNode.nChildren();
+        for (size_t iChild = 0; iChild < num; iChild++) {
             //tranTypeNode is a type of transport property like viscosity
             XML_Node& tranTypeNode = transportNode.child(iChild);
             std::string nodeName = tranTypeNode.name();