diff --git a/simgear/io/sg_serial.hxx b/simgear/io/sg_serial.hxx
index 85a92e1c..e02ace64 100644
--- a/simgear/io/sg_serial.hxx
+++ b/simgear/io/sg_serial.hxx
@@ -40,15 +40,13 @@
 
 #include "iochannel.hxx"
 
-using std::string;
-
 /**
  * A serial I/O class based on SGIOChannel.
  */
 class SGSerial : public SGIOChannel {
 
-    string device;
-    string baud;
+    std::string device;
+    std::string baud;
     SGSerialPort port;
 
     char save_buf[ 2 * SG_IO_MAX_MSG_SIZE ];
@@ -68,7 +66,7 @@ public:
      * @param device_name name of serial device
      * @param baud_rate speed of communication
      */
-    SGSerial( const string& device_name, const string& baud_rate );
+    SGSerial( const std::string& device_name, const std::string& baud_rate );
 
     /** Destructor */
     ~SGSerial();
diff --git a/simgear/math/interpolater.hxx b/simgear/math/interpolater.hxx
index 393e39ff..34dff626 100644
--- a/simgear/math/interpolater.hxx
+++ b/simgear/math/interpolater.hxx
@@ -38,9 +38,7 @@
 #include <simgear/structure/SGReferenced.hxx>
 
 #include <map>
-
 #include <string>
-using std::string;
 
 class SGPropertyNode;
 
@@ -69,7 +67,7 @@ public:
      * Constructor. Loads the interpolation table from the specified file.
      * @param file name of interpolation file
      */
-    SGInterpTable( const string& file );
+    SGInterpTable( const std::string& file );
 
 
     /**
diff --git a/simgear/props/condition.cxx b/simgear/props/condition.cxx
index bfc1bf61..04b892e5 100644
--- a/simgear/props/condition.cxx
+++ b/simgear/props/condition.cxx
@@ -22,6 +22,8 @@
 
 using std::istream;
 using std::ostream;
+using std::string;
+
 /**
  * Condition for a single property.
  *
diff --git a/simgear/scene/material/Technique.cxx b/simgear/scene/material/Technique.cxx
index 3a09dfea..a3c5e34e 100644
--- a/simgear/scene/material/Technique.cxx
+++ b/simgear/scene/material/Technique.cxx
@@ -271,19 +271,19 @@ class ExtensionSupportedExpression
 {
 public:
     ExtensionSupportedExpression() {}
-    ExtensionSupportedExpression(const string& extString)
+    ExtensionSupportedExpression(const std::string& extString)
         : _extString(extString)
     {
     }
-    const string& getExtensionString() { return _extString; }
-    void setExtensionString(const string& extString) { _extString = extString; }
+    const std::string& getExtensionString() { return _extString; }
+    void setExtensionString(const std::string& extString) { _extString = extString; }
     void eval(bool&value, const expression::Binding* b) const
     {
         int contextId = getOperand(0)->getValue(b);
         value = isGLExtensionSupported((unsigned)contextId, _extString.c_str());
     }
 protected:
-    string _extString;
+    std::string _extString;
 };
 
 Expression* extensionSupportedParser(const SGPropertyNode* exp,
diff --git a/simgear/scene/model/SGLightAnimation.cxx b/simgear/scene/model/SGLightAnimation.cxx
index 5806c323..b049c15d 100644
--- a/simgear/scene/model/SGLightAnimation.cxx
+++ b/simgear/scene/model/SGLightAnimation.cxx
@@ -36,7 +36,7 @@
 #include <boost/scoped_array.hpp>
 #include <boost/foreach.hpp>
 
-typedef std::map<string, osg::observer_ptr<simgear::Effect> > EffectMap;
+typedef std::map<std::string, osg::observer_ptr<simgear::Effect> > EffectMap;
 static EffectMap lightEffectMap;
 
 #define GET_COLOR_VALUE(n) \
@@ -96,7 +96,7 @@ public:
 SGLightAnimation::SGLightAnimation(const SGPropertyNode* configNode,
                                    SGPropertyNode* modelRoot,
                                    const osgDB::Options* options,
-                                   const string &path, int i) :
+                                   const std::string &path, int i) :
     SGAnimation(configNode, modelRoot),
     _options(options)
 {
@@ -113,7 +113,7 @@ SGLightAnimation::SGLightAnimation(const SGPropertyNode* configNode,
     _cutoff = getConfig()->getDoubleValue("cutoff");
     _near = getConfig()->getDoubleValue("near-m");
     _far = getConfig()->getDoubleValue("far-m");
-    _key = path + ";" + boost::lexical_cast<string>( i );
+    _key = path + ";" + boost::lexical_cast<std::string>( i );
 
     SGConstPropertyNode_ptr dim_factor = configNode->getChild("dim-factor");
     if (dim_factor.valid()) {
diff --git a/simgear/scene/model/SGMaterialAnimation.hxx b/simgear/scene/model/SGMaterialAnimation.hxx
index 1fe5da8d..bb62e83b 100644
--- a/simgear/scene/model/SGMaterialAnimation.hxx
+++ b/simgear/scene/model/SGMaterialAnimation.hxx
@@ -23,7 +23,7 @@ class SGMaterialAnimation : public SGAnimation {
 public:
   SGMaterialAnimation(const SGPropertyNode* configNode,
                       SGPropertyNode* modelRoot,
-                      const osgDB::Options* options,const string &path);
+                      const osgDB::Options* options,const std::string &path);
   virtual osg::Group* createAnimationGroup(osg::Group& parent);
   virtual void install(osg::Node& node);
   static SGPropertyNode_ptr makeEffectProperties(const SGPropertyNode* animProp);
diff --git a/simgear/scene/model/animation.cxx b/simgear/scene/model/animation.cxx
index fa9931a4..30cab2e3 100644
--- a/simgear/scene/model/animation.cxx
+++ b/simgear/scene/model/animation.cxx
@@ -344,7 +344,7 @@ SGAnimation::~SGAnimation()
   if (!_found)
   {
       std::list<std::string>::const_iterator i;
-      string info;
+      std::string info;
       for (i = _objectNames.begin(); i != _objectNames.end(); ++i)
       {
           if (!info.empty())
@@ -365,7 +365,7 @@ bool
 SGAnimation::animate(osg::Node* node, const SGPropertyNode* configNode,
                      SGPropertyNode* modelRoot,
                      const osgDB::Options* options,
-                     const string &path, int i)
+                     const std::string &path, int i)
 {
   std::string type = configNode->getStringValue("type", "none");
   if (type == "alpha-test") {
diff --git a/simgear/scene/model/animation.hxx b/simgear/scene/model/animation.hxx
index 8cf0b020..048d991f 100644
--- a/simgear/scene/model/animation.hxx
+++ b/simgear/scene/model/animation.hxx
@@ -48,7 +48,7 @@ public:
   static bool animate(osg::Node* node, const SGPropertyNode* configNode,
                       SGPropertyNode* modelRoot,
                       const osgDB::Options* options,
-                      const string &path, int i);
+                      const std::string &path, int i);
 
 protected:
   void apply(osg::Node* node);
@@ -354,11 +354,11 @@ public:
   SGLightAnimation(const SGPropertyNode* configNode,
                    SGPropertyNode* modelRoot,
                    const osgDB::Options* options,
-                   const string &path, int i);
+                   const std::string &path, int i);
   virtual osg::Group* createAnimationGroup(osg::Group& parent);
   virtual void install(osg::Node& node);
 private:
-  string _light_type;
+  std::string _light_type;
   SGVec3d _position;
   SGVec3d _direction;
   SGVec4d _ambient;
@@ -369,7 +369,7 @@ private:
   double _cutoff;
   double _near;
   double _far;
-  string _key;
+  std::string _key;
   class UpdateCallback;
   friend class UpdateCallback;
   SGSharedPtr<SGExpressiond> _animationValue;
diff --git a/simgear/structure/SGExpression.hxx b/simgear/structure/SGExpression.hxx
index 193dbbca..2cfa3dc8 100644
--- a/simgear/structure/SGExpression.hxx
+++ b/simgear/structure/SGExpression.hxx
@@ -26,7 +26,8 @@
 #include <vector>
 #include <functional>
 #include <set>
-   
+#include <string>
+
 #include <simgear/props/condition.hxx>
 #include <simgear/props/props.hxx>
 #include <simgear/math/interpolater.hxx>
@@ -949,7 +950,7 @@ namespace simgear
   {
   struct ParseError : public sg_exception
   {
-      ParseError(const string& message = std::string())
+      ParseError(const std::string& message = std::string())
           : sg_exception(message) {}
   };
     
@@ -1014,7 +1015,7 @@ namespace simgear
   {
   public:
       size_t addBinding(const std::string& name, expression::Type type);
-      bool findBinding(const string& name, VariableBinding& result) const;
+      bool findBinding(const std::string& name, VariableBinding& result) const;
       std::vector<VariableBinding> bindings;
   };
 
@@ -1031,7 +1032,7 @@ namespace simgear
           ParserMap& map = getParserMap();
           ParserMap::iterator itr = map.find(exp->getName());
           if (itr == map.end())
-              throw ParseError(string("unknown expression ") + exp->getName());
+              throw ParseError(std::string("unknown expression ") + exp->getName());
           exp_parser parser = itr->second;
           return (*parser)(exp, this);
       }