diff --git a/lisp/vc/vc.el b/lisp/vc/vc.el
index 14b149310c..2867539aa3 100644
--- a/lisp/vc/vc.el
+++ b/lisp/vc/vc.el
@@ -1926,6 +1926,13 @@ vc-revision-history
   "History for `vc-read-revision'.")
 
 (defun vc-read-revision (prompt &optional files backend default initial-input multiple)
+  "Query the user for a revision using PROMPT.
+All subsequent arguments are optional.  FILES may specify a file
+set to restrict the revisions to.  BACKEND is a VC backend as
+listed in `vc-handled-backends'.  DEFAULT and INITIAL-INPUT are
+handled as defined by `completing-read'.  If MULTIPLE is non-nil,
+the user may be prompted for multiple revisions.  If possible
+this means that `completing-read-multiple' will be used."
   (cond
    ((null files)
     (let ((vc-fileset (vc-deduce-fileset t))) ;FIXME: why t?  --Stef
@@ -1947,6 +1954,10 @@ vc-read-revision
           answer)))))
 
 (defun vc-read-multiple-revisions (prompt &optional files backend default initial-input)
+  "Query the user for multiple revisions.
+This is equivalent to invoking `vc-read-revision' with t for
+MULTIPLE.  The arguments PROMPT, FILES, BACKEND, DEFAULT and
+INITIAL-INPUT are passed on to `vc-read-revision' directly."
   (vc-read-revision prompt files backend default initial-input t))
 
 (defun vc-diff-build-argument-list-internal (&optional fileset)