diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 30055bf16d5..855b53ab908 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,7 @@
+2008-06-28  John Paul Wallington  <jpw@pobox.com>
+
+	* calc/calc.el (defmath): Add `doc-string' decl.  Add docstring.
+
 2008-06-28  Michael Albinus  <michael.albinus@gmx.de>
 
 	* net/tramp.el (tramp-handle-file-modes): Handle symlinks.
diff --git a/lisp/calc/calc.el b/lisp/calc/calc.el
index f1fc2c411a0..0721e8a983f 100644
--- a/lisp/calc/calc.el
+++ b/lisp/calc/calc.el
@@ -3663,6 +3663,17 @@ Also looks for the equivalent TeX words, \\gets and \\evalto."
 
 ;;;###autoload
 (defmacro defmath (func args &rest body)   ;  [Public]
+  "Define Calc function.
+
+Like `defun' except that code in the body of the definition can
+make use of the full range of Calc data types and the usual
+arithmetic operations are converted to their Calc equivalents.
+
+The prefix `calcFunc-' is added to the specified name to get the
+actual Lisp function name.
+
+See Info node `(calc)Defining Functions'."
+  (declare (doc-string 3))
   (require 'calc-ext)
   (math-do-defmath func args body))