--- users_guide.in.orig	2008-08-20 00:34:57.000000000 -0400
+++ users_guide.in	2009-07-08 22:32:17.000000000 -0400
@@ -164,7 +164,10 @@ for S/KEY in the Makefile.  I got my S/K
 crimelab.com but now it appears the only source is ftp.bellcore.com. I
 suggest you try a web search for s/key source code.
 
-Note: S/KEY is a trademark of Bell Communications Research (Bellcore).
+To use OPIE, you must have built tac_plus with the -DWITH_OPIE flag.
+
+Note: S/KEY and OPIE are a trademark of Bell Communications Research 
+(Bellcore).
 
 Should you need them, there are routines for accessing password files
 (getpwnam,setpwent,endpwent,setpwfile) in pw.c.
@@ -454,6 +457,15 @@ be that for each authentiction that is a
 to be wrong whether it was typed correctly or not.
 
 
+4. Authentication using opie.
+
+If you have successfully built tac_plus with opie support, you can specify
+a user be authenticated via opie, as follows:
+
+    user = marcus {
+      login = opie
+    }
+
 RECURSIVE PASSWORD LOOKUPS
 ---------------------------