diff --git a/src/SMESH/SMESH_Mesh.cxx b/src/SMESH/SMESH_Mesh.cxx
index ef500ac8e..eb0f0392d 100644
--- a/src/SMESH/SMESH_Mesh.cxx
+++ b/src/SMESH/SMESH_Mesh.cxx
@@ -33,6 +33,7 @@
 #include "SMESH_Group.hxx"
 #include "SMESHDS_Group.hxx"
 #include "SMESHDS_Script.hxx"
+#include "SMESHDS_GroupOnGeom.hxx"
 #include "SMDS_MeshVolume.hxx"
 
 #include "utilities.h"
@@ -110,15 +111,39 @@ SMESH_Mesh::~SMESH_Mesh()
  */
 //=============================================================================
 
-void SMESH_Mesh::ShapeToMesh(const TopoDS_Shape & aShape){
+void SMESH_Mesh::ShapeToMesh(const TopoDS_Shape & aShape)
+{
   if(MYDEBUG) MESSAGE("SMESH_Mesh::ShapeToMesh");
-  if (_isShapeToMesh)
-    throw
-      SALOME_Exception(LOCALIZED
-		       ("a shape to mesh as already been defined"));
+
+  if ( !_myMeshDS->ShapeToMesh().IsNull() && aShape.IsNull() )
+  {
+    // removal of a shape to mesh, delete objects referring to sub-shapes:
+    // - sub-meshes
+    map <int, SMESH_subMesh *>::iterator i_sm = _mapSubMesh.begin();
+    for ( ; i_sm != _mapSubMesh.end(); ++i_sm )
+      delete i_sm->second;
+    _mapSubMesh.clear();
+    //  - groups on geometry
+    map <int, SMESH_Group *>::iterator i_gr = _mapGroup.begin();
+    while ( i_gr != _mapGroup.end() ) {
+      if ( dynamic_cast<SMESHDS_GroupOnGeom*>( i_gr->second->GetGroupDS() )) {
+        _myMeshDS->RemoveGroup( i_gr->second->GetGroupDS() );
+        delete i_gr->second;
+        _mapGroup.erase( i_gr++ );
+      }
+      else
+        i_gr++;
+    }
+    _mapAncestors.Clear();
+    _mapPropagationChains.Clear();
+  }
+  else
+  {
+    if (_isShapeToMesh)
+      throw SALOME_Exception(LOCALIZED ("a shape to mesh has already been defined"));
+  }
   _isShapeToMesh = true;
   _myMeshDS->ShapeToMesh(aShape);
-  
   // NRI : 24/02/03
   //EAP: 1/9/04 TopExp::MapShapes(aShape, _subShapes); USE the same map of _myMeshDS
 }
@@ -132,7 +157,7 @@ int SMESH_Mesh::UNVToMesh(const char* theFileName)
 {
   if(MYDEBUG) MESSAGE("UNVToMesh - theFileName = "<<theFileName);
   if(_isShapeToMesh)
-    throw SALOME_Exception(LOCALIZED("a shape to mesh as already been defined"));
+    throw SALOME_Exception(LOCALIZED("a shape to mesh has already been defined"));
   _isShapeToMesh = true;
   DriverUNV_R_SMDS_Mesh myReader;
   myReader.SetMesh(_myMeshDS);
@@ -157,7 +182,7 @@ int SMESH_Mesh::MEDToMesh(const char* theFileName, const char* theMeshName)
 {
   if(MYDEBUG) MESSAGE("MEDToMesh - theFileName = "<<theFileName<<", mesh name = "<<theMeshName);
   if(_isShapeToMesh)
-    throw SALOME_Exception(LOCALIZED("a shape to mesh as already been defined"));
+    throw SALOME_Exception(LOCALIZED("a shape to mesh has already been defined"));
   _isShapeToMesh = true;
   DriverMED_R_SMESHDS_Mesh myReader;
   myReader.SetMesh(_myMeshDS);
@@ -199,7 +224,7 @@ int SMESH_Mesh::STLToMesh(const char* theFileName)
 {
   if(MYDEBUG) MESSAGE("UNVToMesh - theFileName = "<<theFileName);
   if(_isShapeToMesh)
-    throw SALOME_Exception(LOCALIZED("a shape to mesh as already been defined"));
+    throw SALOME_Exception(LOCALIZED("a shape to mesh has already been defined"));
   _isShapeToMesh = true;
   DriverSTL_R_SMDS_Mesh myReader;
   myReader.SetMesh(_myMeshDS);
diff --git a/src/SMESHDS/SMESHDS_Mesh.cxx b/src/SMESHDS/SMESHDS_Mesh.cxx
index f0fa21912..416da54aa 100644
--- a/src/SMESHDS/SMESHDS_Mesh.cxx
+++ b/src/SMESHDS/SMESHDS_Mesh.cxx
@@ -32,6 +32,7 @@
 #include "SMDS_VertexPosition.hxx"
 #include "SMDS_EdgePosition.hxx"
 #include "SMDS_FacePosition.hxx"
+#include "SMESHDS_GroupOnGeom.hxx"
 #include <TopExp_Explorer.hxx>
 #include <TopExp.hxx>
 #include <TopoDS_Iterator.hxx>
@@ -55,8 +56,37 @@ SMESHDS_Mesh::SMESHDS_Mesh(int MeshID):myMeshID(MeshID)
 //=======================================================================
 void SMESHDS_Mesh::ShapeToMesh(const TopoDS_Shape & S)
 {
-	myShape = S;
-	TopExp::MapShapes(myShape, myIndexToShape);
+  if ( !myShape.IsNull() && S.IsNull() )
+  {
+    // removal of a shape to mesh, delete ...
+    // - hypotheses
+    myShapeToHypothesis.clear();
+    // - shape indices in SMDS_Position of nodes
+    map<int,SMESHDS_SubMesh*>::iterator i_sub = myShapeIndexToSubMesh.begin();
+    for ( ; i_sub != myShapeIndexToSubMesh.end(); i_sub++ ) {
+      if ( !i_sub->second->IsComplexSubmesh() ) {
+        SMDS_NodeIteratorPtr nIt = i_sub->second->GetNodes();
+        while ( nIt->more() )
+          nIt->next()->GetPosition()->SetShapeId( 0 );
+      }
+    }
+    // - sub-meshes
+    myIndexToShape.Clear();
+    myShapeIndexToSubMesh.clear();
+    // - groups on geometry
+    set<SMESHDS_GroupBase*>::iterator gr = myGroups.begin();
+    while ( gr != myGroups.end() ) {
+      if ( dynamic_cast<SMESHDS_GroupOnGeom*>( *gr ))
+        myGroups.erase( gr++ );
+      else
+        gr++;
+    }
+  }
+  else {
+    myShape = S;
+    if ( !S.IsNull() )
+      TopExp::MapShapes(myShape, myIndexToShape);
+  }
 }
 
 //=======================================================================