diff --git a/doc/emacs/rmail.texi b/doc/emacs/rmail.texi
index e38bde036a..4939f5597c 100644
--- a/doc/emacs/rmail.texi
+++ b/doc/emacs/rmail.texi
@@ -1409,6 +1409,13 @@ Rmail Rot13
 rot13-other-window}.  This displays the current buffer in another window
 which applies the code when displaying the text.
 
+@findex rot13-region
+  If you are only interested in a region, the command @kbd{M-x
+rot13-region} might be preferable.  This will decrypt the active
+region in place.  If the buffer is read-only, it will attempt to
+display the plain text in the echo area.  If the text is too long, a
+separate buffer will be used.
+
 @node Movemail
 @section @command{movemail} program
 @cindex @command{movemail} program