Index: genshi/template/tests/directives.py
===================================================================
--- genshi/template/tests/directives.py	(revision 1064)
+++ genshi/template/tests/directives.py	(working copy)
@@ -59,6 +59,32 @@
         </doc>""", str(tmpl.generate()))
 
 
+class CommentDirectiveTestCase(unittest.TestCase):
+    """Tests for the `py:comment` template directive."""
+
+    def test_comment_processes(self):
+        tmpl = MarkupTemplate("""<div xmlns:py="http://genshi.edgewall.org/">
+          <py:comment>${1 + 1}</py:comment>
+        </div>""")
+        self.assertEqual("""<div>
+          <!--2-->
+        </div>""", str(tmpl.generate()))
+
+    def test_comment_empty(self):
+        tmpl = MarkupTemplate("""<div xmlns:py="http://genshi.edgewall.org/">
+          <py:comment />
+        </div>""")
+        self.assertEqual("""<div>
+          <!---->
+        </div>""", str(tmpl.generate()))
+
+    def test_comment_not_attribute(self):
+        tmpl = MarkupTemplate("""<div xmlns:py="http://genshi.edgewall.org/">
+          <p py:comment=""></p>
+        </div>""")
+        self.assertRaises(TemplateSyntaxError, tmpl.generate)
+
+
 class ChooseDirectiveTestCase(unittest.TestCase):
     """Tests for the `py:choose` template directive and the complementary
     directives `py:when` and `py:otherwise`."""
@@ -1134,6 +1160,7 @@
     suite.addTest(doctest.DocTestSuite(directives))
     suite.addTest(unittest.makeSuite(AttrsDirectiveTestCase, 'test'))
     suite.addTest(unittest.makeSuite(ChooseDirectiveTestCase, 'test'))
+    suite.addTest(unittest.makeSuite(CommentDirectiveTestCase, 'test'))
     suite.addTest(unittest.makeSuite(DefDirectiveTestCase, 'test'))
     suite.addTest(unittest.makeSuite(ForDirectiveTestCase, 'test'))
     suite.addTest(unittest.makeSuite(IfDirectiveTestCase, 'test'))
Index: genshi/template/markup.py
===================================================================
--- genshi/template/markup.py	(revision 1064)
+++ genshi/template/markup.py	(working copy)
@@ -56,6 +56,7 @@
                   ('replace', ReplaceDirective),
                   ('content', ContentDirective),
                   ('attrs', AttrsDirective),
+                  ('comment', CommentDirective),
                   ('strip', StripDirective)]
     serializer = 'xml'
     _number_conv = Markup
Index: genshi/template/directives.py
===================================================================
--- genshi/template/directives.py	(revision 1064)
+++ genshi/template/directives.py	(working copy)
@@ -13,7 +13,7 @@
 
 """Implementation of the various template directives."""
 
-from genshi.core import QName, Stream
+from genshi.core import QName, Stream, TEXT, Markup
 from genshi.path import Path
 from genshi.template.base import TemplateRuntimeError, TemplateSyntaxError, \
                                  EXPR, _apply_directives, _eval_expr
@@ -21,7 +21,8 @@
                                  _ast, _parse
 
 __all__ = ['AttrsDirective', 'ChooseDirective', 'ContentDirective',
-           'DefDirective', 'ForDirective', 'IfDirective', 'MatchDirective',
+           'CommentDirective', 'DefDirective', 'ForDirective', 
+           'IfDirective', 'MatchDirective',
            'OtherwiseDirective', 'ReplaceDirective', 'StripDirective',
            'WhenDirective', 'WithDirective']
 __docformat__ = 'restructuredtext en'
@@ -185,6 +186,41 @@
         return _apply_directives(_generate(), directives, ctxt, vars)
 
 
+class CommentDirective(Directive):
+    """Implementation of the ``py:comment`` template directive.
+    
+    This directive replaces the content of the element with the result of
+    evaluating the value of the ``py:comment`` attribute:
+    
+    >>> from genshi.template import MarkupTemplate
+    >>> tmpl = MarkupTemplate('''<div xmlns:py="http://genshi.edgewall.org/">
+    ...   <py:comment>${2 + 2}</py:comment>
+    ... </div>''')
+    >>> print tmpl.generate(bar='Bye')
+    <div>
+      <!--4-->
+    </div>
+    """
+    __slots__ = []
+
+    @classmethod
+    def attach(cls, template, stream, value, namespaces, pos):
+        if type(value) is not dict:
+            raise TemplateSyntaxError('The comment directive can only be used '
+                                      'as an element', template.filepath,
+                                      *pos[1:])
+        return super(CommentDirective, cls).attach(template, stream,
+                                                   value, namespaces, pos)
+
+    def __call__(self, stream, directives, ctxt, **vars):
+        stream = list(stream)
+        
+        stream.insert(0, (TEXT, Markup("<!--"), (None, 1, 0)))
+        stream.append((TEXT, Markup("-->"), (None, 1, 0)))
+        
+        return _apply_directives(stream, directives, ctxt, vars)
+
+
 class ContentDirective(Directive):
     """Implementation of the ``py:content`` template directive.