diff --git a/IPython/html/nbconvert/handlers.py b/IPython/html/nbconvert/handlers.py
index 749cd9d..63ba266 100644
--- a/IPython/html/nbconvert/handlers.py
+++ b/IPython/html/nbconvert/handlers.py
@@ -43,7 +43,7 @@ def respond_zip(handler, name, output, resources):
     # Prepare the zip file
     buffer = io.BytesIO()
     zipf = zipfile.ZipFile(buffer, mode='w', compression=zipfile.ZIP_DEFLATED)
-    output_filename = os.path.splitext(name)[0] + '.' + resources['output_extension']
+    output_filename = os.path.splitext(name)[0] + resources['output_extension']
     zipf.writestr(output_filename, cast_bytes(output, 'utf-8'))
     for filename, data in output_files.items():
         zipf.writestr(os.path.basename(filename), data)
@@ -96,7 +96,7 @@ class NbconvertFileHandler(IPythonHandler):
 
         # Force download if requested
         if self.get_argument('download', 'false').lower() == 'true':
-            filename = os.path.splitext(name)[0] + '.' + resources['output_extension']
+            filename = os.path.splitext(name)[0] + resources['output_extension']
             self.set_header('Content-Disposition',
                                'attachment; filename="%s"' % filename)
 
diff --git a/IPython/html/static/notebook/js/menubar.js b/IPython/html/static/notebook/js/menubar.js
index 8350fc2..9a2814b 100644
--- a/IPython/html/static/notebook/js/menubar.js
+++ b/IPython/html/static/notebook/js/menubar.js
@@ -359,7 +359,7 @@ define([
         // Set menu entry text to e.g. "Python (.py)"
         var langname = (langinfo.name || 'Script')
         langname = langname.charAt(0).toUpperCase()+langname.substr(1) // Capitalise
-        el.find('a').text(langname + ' (.'+(langinfo.file_extension || 'txt')+')');
+        el.find('a').text(langname + ' ('+(langinfo.file_extension || 'txt')+')');
         
         // Unregister any previously registered handlers
         el.off('click');
diff --git a/IPython/kernel/zmq/ipkernel.py b/IPython/kernel/zmq/ipkernel.py
index 1ef8975..5cc0a01 100644
--- a/IPython/kernel/zmq/ipkernel.py
+++ b/IPython/kernel/zmq/ipkernel.py
@@ -76,7 +76,7 @@ class IPythonKernel(KernelBase):
                                          'version': sys.version_info[0]},
                      'pygments_lexer': 'ipython%d' % (3 if PY3 else 2),
                      'nbconvert_exporter': 'python',
-                     'file_extension': 'py'
+                     'file_extension': '.py'
                     }
     @property
     def banner(self):
diff --git a/IPython/nbconvert/exporters/exporter.py b/IPython/nbconvert/exporters/exporter.py
index a6c00fd..33991db 100644
--- a/IPython/nbconvert/exporters/exporter.py
+++ b/IPython/nbconvert/exporters/exporter.py
@@ -32,7 +32,7 @@ class Exporter(LoggingConfigurable):
     """
 
     file_extension = Unicode(
-        'txt', config=True,
+        '.txt', config=True,
         help="Extension of the file that should be written to disk"
         )
 
diff --git a/IPython/nbconvert/exporters/html.py b/IPython/nbconvert/exporters/html.py
index 3df3810..d833691 100644
--- a/IPython/nbconvert/exporters/html.py
+++ b/IPython/nbconvert/exporters/html.py
@@ -32,7 +32,7 @@ class HTMLExporter(TemplateExporter):
     """
     
     def _file_extension_default(self):
-        return 'html'
+        return '.html'
 
     def _default_template_path_default(self):
         return os.path.join("..", "templates", "html")
diff --git a/IPython/nbconvert/exporters/pdf.py b/IPython/nbconvert/exporters/pdf.py
index 0ef2b2d..d79610b 100644
--- a/IPython/nbconvert/exporters/pdf.py
+++ b/IPython/nbconvert/exporters/pdf.py
@@ -135,7 +135,7 @@ class PDFExporter(LatexExporter):
         
         # convert output extension to pdf
         # the writer above required it to be tex
-        resources['output_extension'] = 'pdf'
+        resources['output_extension'] = '.pdf'
         
         return pdf_data, resources
     
diff --git a/IPython/nbconvert/exporters/python.py b/IPython/nbconvert/exporters/python.py
index 5c7dbf4..e1218da 100644
--- a/IPython/nbconvert/exporters/python.py
+++ b/IPython/nbconvert/exporters/python.py
@@ -23,7 +23,7 @@ class PythonExporter(TemplateExporter):
     Exports a Python code file.
     """
     def _file_extension_default(self):
-        return 'py'
+        return '.py'
 
     def _template_file_default(self):
         return 'python'
diff --git a/IPython/nbconvert/exporters/rst.py b/IPython/nbconvert/exporters/rst.py
index eaae267..731e978 100644
--- a/IPython/nbconvert/exporters/rst.py
+++ b/IPython/nbconvert/exporters/rst.py
@@ -26,7 +26,7 @@ class RSTExporter(TemplateExporter):
     """
     
     def _file_extension_default(self):
-        return 'rst'
+        return '.rst'
 
     def _template_file_default(self):
         return 'rst'
diff --git a/IPython/nbconvert/exporters/script.py b/IPython/nbconvert/exporters/script.py
index d89eb80..2e1148a 100644
--- a/IPython/nbconvert/exporters/script.py
+++ b/IPython/nbconvert/exporters/script.py
@@ -8,7 +8,7 @@ class ScriptExporter(TemplateExporter):
 
     def from_notebook_node(self, nb, resources=None, **kw):
         langinfo = nb.metadata.get('language_info', {})
-        self.file_extension = langinfo.get('file_extension', 'txt')
+        self.file_extension = langinfo.get('file_extension', '.txt')
         self.output_mimetype = langinfo.get('mimetype', 'text/plain')
 
         return super(ScriptExporter, self).from_notebook_node(nb, resources, **kw)
diff --git a/IPython/nbconvert/nbconvertapp.py b/IPython/nbconvert/nbconvertapp.py
index 1e252d0..115b645 100755
--- a/IPython/nbconvert/nbconvertapp.py
+++ b/IPython/nbconvert/nbconvertapp.py
@@ -286,7 +286,7 @@ class NbConvertApp(BaseIPythonApplication):
                 # strip duplicate extension from output_base, to avoid Basname.ext.ext
                 if getattr(exporter, 'file_extension', False):
                     base, ext = os.path.splitext(self.output_base)
-                    if ext == '.' + exporter.file_extension:
+                    if ext == exporter.file_extension:
                         self.output_base = base
                 notebook_name = self.output_base
             resources = {}
diff --git a/IPython/nbconvert/writers/files.py b/IPython/nbconvert/writers/files.py
index 01062e2..d124fb9 100644
--- a/IPython/nbconvert/writers/files.py
+++ b/IPython/nbconvert/writers/files.py
@@ -93,7 +93,7 @@ class FilesWriter(WriterBase):
 
             # Determine where to write conversion results.
             if output_extension is not None:
-                dest = notebook_name + '.' + output_extension
+                dest = notebook_name + output_extension
             else:
                 dest = notebook_name
             if self.build_directory:
diff --git a/IPython/nbconvert/writers/tests/test_files.py b/IPython/nbconvert/writers/tests/test_files.py
index a859a85..38793d1 100644
--- a/IPython/nbconvert/writers/tests/test_files.py
+++ b/IPython/nbconvert/writers/tests/test_files.py
@@ -59,7 +59,7 @@ class Testfiles(TestsBase):
         with self.create_temp_cwd():
 
             # Create the resoruces dictionary
-            res = {'output_extension': 'txt'}
+            res = {'output_extension': '.txt'}
 
             # Create files writer, test output
             writer = FilesWriter()