--- a/doc/setup.txt
+++ b/doc/setup.txt
@@ -21,7 +21,7 @@
         ...
         cmd_class = {'compile_catalog': babel.compile_catalog,
                      'extract_messages': babel.extract_messages,
-                     'new_catalog': babel.new_catalog}
+                     'init_catalog': babel.init_catalog}
     )
 
 
@@ -214,37 +214,37 @@
 file. For boolean options, use "true" or "false" values.
 
 
-new_catalog
-===========
+init_catalog
+============
 
-The ``new_catalog`` command is basically equivalent to the GNU ``msginit``
+The ``init_catalog`` command is basically equivalent to the GNU ``msginit``
 program: it creates a new translation catalog based on a PO template file (POT).
 
 If the command has been correctly installed or registered, a project's
 ``setup.py`` script should allow you to use the command::
 
-    $ ./setup.py new_catalog --help
+    $ ./setup.py init_catalog --help
     Global options:
       --verbose (-v)  run verbosely (default)
       --quiet (-q)    run quietly (turns verbosity off)
       --dry-run (-n)  don't actually do anything
       --help (-h)     show detailed help message
 
-    Options for 'new_catalog' command:
+    Options for 'init_catalog' command:
       ...
 
 Running the command will produce a PO file::
 
-    $ ./setup.py new_catalog -l fr -i foobar/locales/messages.pot \
+    $ ./setup.py init_catalog -l fr -i foobar/locales/messages.pot \
                              -o foobar/locales/fr/messages.po
-    running new_catalog
+    running init_catalog
     creating catalog 'foobar/locales/fr/messages.po' based on 'foobar/locales/messages.pot'
 
 
 Options
 -------
 
-The ``new_catalog`` command accepts the following options:
+The ``init_catalog`` command accepts the following options:
 
   +-----------------------------+----------------------------------------------+
   | Option                      | Description                                  |
@@ -274,3 +274,64 @@
 
 These options can either be specified on the command-line, or in the
 ``setup.cfg`` file.
+
+
+update_catalog
+==============
+
+The ``update_catalog`` command is basically equivalent to the GNU ``msgmerge``
+program: it updates an existing translations catalog based on a PO template
+file (POT).
+
+If the command has been correctly installed or registered, a project's
+``setup.py`` script should allow you to use the command::
+
+    $ ./setup.py update_catalog --help
+    Global options:
+      --verbose (-v)  run verbosely (default)
+      --quiet (-q)    run quietly (turns verbosity off)
+      --dry-run (-n)  don't actually do anything
+      --help (-h)     show detailed help message
+
+    Options for 'update_catalog' command:
+      ...
+
+Running the command will update a PO file::
+
+    $ ./setup.py update_catalog -l fr -i foobar/locales/messages.pot \
+                                -o foobar/locales/fr/messages.po
+    running update_catalog
+    updating catalog 'foobar/locales/fr/messages.po' based on 'foobar/locales/messages.pot'
+
+
+Options
+-------
+
+The ``update_catalog`` command accepts the following options:
+
+  +-----------------------------+----------------------------------------------+
+  | Option                      | Description                                  |
+  +=============================+==============================================+
+  | ``--domain``                | domain of the PO file (defaults to           |
+  |                             | lower-cased project name)                    |
+  +-----------------------------+----------------------------------------------+
+  | ``--input-file`` (``-i``)   | name of the input file                       |
+  +-----------------------------+----------------------------------------------+
+  | ``--output-dir`` (``-d``)   | name of the output directory                 |
+  +-----------------------------+----------------------------------------------+
+  | ``--output-file`` (``-o``)  | name of the output file                      |
+  +-----------------------------+----------------------------------------------+
+  | ``--locale``                | locale for the new localized string          |
+  +-----------------------------+----------------------------------------------+
+
+If ``output-dir`` is specified, but ``output-file`` is not, the default filename
+of the output file will be::
+
+    <output_dir>/<locale>/LC_MESSAGES/<domain>.po
+
+If neither the ``input_file`` nor the ``locale`` option is set, this command
+looks for all catalog files in the base directory that match the given domain,
+and updates each of them.
+
+These options can either be specified on the command-line, or in the
+``setup.cfg`` file.