diff --git a/elab_scope.cc b/elab_scope.cc
index f9753fa77..a0f4c10c2 100644
--- a/elab_scope.cc
+++ b/elab_scope.cc
@@ -349,13 +349,33 @@ static void blend_class_constructors(PClass*pclass)
 static void elaborate_scope_class(Design*des, NetScope*scope, PClass*pclass)
 {
       class_type_t*use_type = pclass->type;
-      netclass_t*use_class = new netclass_t(use_type->name);
 
       if (debug_scopes) {
 	    cerr << pclass->get_fileline() <<": elaborate_scope_class: "
 		 << "Elaborate scope class " << pclass->pscope_name() << endl;
       }
 
+      class_type_t*base_class = dynamic_cast<class_type_t*> (use_type->base_type);
+      if (use_type->base_type && !base_class) {
+	    cerr << pclass->get_fileline() << ": error: "
+		 << "Base type of " << use_type->name
+		 << " is not a class." << endl;
+	    des->errors += 1;
+      }
+
+      netclass_t*use_base_class = 0;
+      if (base_class) {
+	    use_base_class = scope->find_class(base_class->name);
+	    if (use_base_class == 0) {
+		  cerr << pclass->get_fileline() << ": error: "
+		       << "Base class " << base_class->name
+		       << " not found." << endl;
+		  des->errors += 1;
+	    }
+      }
+
+      netclass_t*use_class = new netclass_t(use_type->name, use_base_class);
+
 	// Class scopes have no parent scope, because references are
 	// not allowed to escape a class method.
       NetScope*class_scope = new NetScope(0, hname_t(pclass->pscope_name()),
diff --git a/netclass.cc b/netclass.cc
index 7f2fb97d3..f302585d1 100644
--- a/netclass.cc
+++ b/netclass.cc
@@ -23,8 +23,8 @@
 
 using namespace std;
 
-netclass_t::netclass_t(perm_string name)
-: name_(name), class_scope_(0)
+netclass_t::netclass_t(perm_string name, netclass_t*sup)
+: name_(name), super_(sup), class_scope_(0)
 {
 }
 
@@ -61,43 +61,85 @@ ivl_variable_type_t netclass_t::base_type() const
       return IVL_VT_CLASS;
 }
 
+size_t netclass_t::get_properties(void) const
+{
+      size_t res = properties_.size();
+      if (super_) res += super_->get_properties();
+      return res;
+}
+
 int netclass_t::property_idx_from_name(perm_string pname) const
 {
       map<perm_string,size_t>::const_iterator cur;
       cur = properties_.find(pname);
-      if (cur == properties_.end())
-	    return -1;
+      if (cur == properties_.end()) {
+	    if (super_)
+		  return super_->property_idx_from_name(pname);
+	    else
+		  return -1;
+      }
 
-      return cur->second;
+      int pidx = cur->second;
+      if (super_) pidx += super_->get_properties();
+      return pidx;
 }
 
 const char*netclass_t::get_prop_name(size_t idx) const
 {
-      assert(idx < property_table_.size());
-      return property_table_[idx].name;
+      size_t super_size = 0;
+      if (super_) super_size = super_->get_properties();
+
+      assert(idx < (super_size + property_table_.size()));
+      if (idx < super_size)
+	    return super_->get_prop_name(idx);
+      else
+	    return property_table_[idx-super_size].name;
 }
 
 property_qualifier_t netclass_t::get_prop_qual(size_t idx) const
 {
-      assert(idx < property_table_.size());
-      return property_table_[idx].qual;
+      size_t super_size = 0;
+      if (super_) super_size = super_->get_properties();
+
+      assert(idx < (super_size+property_table_.size()));
+      if (idx < super_size)
+	    return super_->get_prop_qual(idx);
+      else
+	    return property_table_[idx-super_size].qual;
 }
 
 ivl_type_t netclass_t::get_prop_type(size_t idx) const
 {
-      assert(idx < property_table_.size());
-      return property_table_[idx].type;
+      size_t super_size = 0;
+      if (super_) super_size = super_->get_properties();
+
+      assert(idx < (super_size+property_table_.size()));
+      if (idx < super_size)
+	    return super_->get_prop_type(idx);
+      else
+	    return property_table_[idx-super_size].type;
 }
 
 bool netclass_t::get_prop_initialized(size_t idx) const
 {
-      assert(idx < property_table_.size());
-      return property_table_[idx].initialized_flag;
+      size_t super_size = 0;
+      if (super_) super_size = super_->get_properties();
+
+      assert(idx < (super_size+property_table_.size()));
+      if (idx < super_size)
+	    return super_->get_prop_initialized(idx);
+      else
+	    return property_table_[idx].initialized_flag;
 }
 
 void netclass_t::set_prop_initialized(size_t idx) const
 {
-      assert(idx < property_table_.size());
+      size_t super_size = 0;
+      if (super_) super_size = super_->get_properties();
+
+      assert(idx >= super_size && idx < (super_size+property_table_.size()));
+      idx -= super_size;
+
       assert(! property_table_[idx].initialized_flag);
       property_table_[idx].initialized_flag = true;
 }
diff --git a/netclass.h b/netclass.h
index 56039a56c..79e912f74 100644
--- a/netclass.h
+++ b/netclass.h
@@ -33,7 +33,7 @@ class PClass;
 
 class netclass_t : public ivl_type_s {
     public:
-      netclass_t(perm_string class_name);
+      netclass_t(perm_string class_name, netclass_t*par);
       ~netclass_t();
 
 	// Set the property of the class during elaboration. Set the
@@ -52,7 +52,13 @@ class netclass_t : public ivl_type_s {
 	// This is the name of the class type
       inline perm_string get_name() const { return name_; }
 
-      inline size_t get_properties(void) const { return properties_.size(); }
+	// If this is derived from another class, then this method
+	// returns a pointer to the super-class.
+      inline const netclass_t* get_super() const { return super_; }
+
+	// Get the number of properties in this class. Include
+	// properties in the parent class.
+      size_t get_properties(void) const;
 	// Get information about each property.
       const char*get_prop_name(size_t idx) const;
       property_qualifier_t get_prop_qual(size_t idx) const;
@@ -92,6 +98,9 @@ class netclass_t : public ivl_type_s {
 
     private:
       perm_string name_;
+	// If this is derived from another base class, point to it
+	// here.
+      netclass_t*super_;
 	// Map properrty names to property table index.
       std::map<perm_string,size_t> properties_;
 	// Vector of properties.
diff --git a/parse.y b/parse.y
index 393aa6d10..5baf61dc7 100644
--- a/parse.y
+++ b/parse.y
@@ -683,11 +683,7 @@ assignment_pattern /* IEEE1800-2005: A.6.7.1 */
 
 class_declaration /* IEEE1800-2005: A.1.2 */
   : K_virtual_opt K_class class_identifier class_declaration_extends_opt ';'
-      { pform_start_class_declaration(@2, $3);
-	if ($4) {
-	      yyerror(@4, "sorry: Class extends not supported yet.");
-	}
-      }
+      { pform_start_class_declaration(@2, $3, $4); }
     class_items_opt K_endclass
       { // Process a class.
 	pform_end_class_declaration(@8);
diff --git a/pform.h b/pform.h
index 6eaf170ff..70db36c87 100644
--- a/pform.h
+++ b/pform.h
@@ -181,7 +181,8 @@ extern void pform_endmodule(const char*, bool inside_celldefine,
                             Module::UCDriveType uc_drive_def);
 
 extern void pform_start_class_declaration(const struct vlltype&loc,
-					  class_type_t*type);
+					  class_type_t*type,
+					  data_type_t*base_type);
 extern void pform_class_property(const struct vlltype&loc,
 				 property_qualifier_t pq,
 				 data_type_t*data_type,
diff --git a/pform_dump.cc b/pform_dump.cc
index a744b3c96..9a02c9d2d 100644
--- a/pform_dump.cc
+++ b/pform_dump.cc
@@ -182,12 +182,16 @@ void class_type_t::pform_dump(ostream&out, unsigned indent) const
 {
       out << setw(indent) << "" << "class " << name << " {";
 
+      if (base_type) out << " (extends)";
+
       for (map<perm_string,prop_info_t>::const_iterator cur = properties.begin()
 		 ; cur != properties.end() ; ++cur) {
 	    out << " " << cur->first;
       }
 
       out << " }" << endl;
+
+      if (base_type) base_type->pform_dump(out, indent+4);
 }
 
 void class_type_t::pform_dump_init(ostream&out, unsigned indent) const
diff --git a/pform_pclass.cc b/pform_pclass.cc
index f82b8120b..f3da71dda 100644
--- a/pform_pclass.cc
+++ b/pform_pclass.cc
@@ -26,12 +26,15 @@
  */
 static PClass*pform_cur_class = 0;
 
-void pform_start_class_declaration(const struct vlltype&loc, class_type_t*type)
+void pform_start_class_declaration(const struct vlltype&loc, class_type_t*type, data_type_t*base_type)
 {
       PClass*class_scope = pform_push_class_scope(loc, type->name);
       class_scope->type = type;
       assert(pform_cur_class == 0);
       pform_cur_class = class_scope;
+
+      assert(type->base_type == 0);
+      type->base_type = base_type;
 }
 
 void pform_class_property(const struct vlltype&loc,
diff --git a/pform_types.h b/pform_types.h
index f8ba0e172..5619e6d39 100644
--- a/pform_types.h
+++ b/pform_types.h
@@ -225,13 +225,19 @@ struct string_type_t : public data_type_t {
 struct class_type_t : public data_type_t {
 
       inline explicit class_type_t(perm_string n)
-      : name(n) { }
+      : name(n), base_type(0) { }
 
       void pform_dump(std::ostream&out, unsigned indent) const;
       void pform_dump_init(std::ostream&out, unsigned indent) const;
 
 	// This is the name of the class type.
       perm_string name;
+
+	// This is the named type that is supposed to be the base
+	// class that we are extending. This is nil if there is no
+	// hierarchy.
+      data_type_t*base_type;
+
 	// This is a map of the properties. Map the name to the type.
       struct prop_info_t {
 	    inline prop_info_t() : qual(property_qualifier_t::make_none()), type(0) { }