diff --git a/man/man1/mred.1 b/man/man1/mred.1
index ff482f89..68c8d2de 100644
--- a/man/man1/mred.1
+++ b/man/man1/mred.1
@@ -66,6 +66,15 @@ When running in X11, MrEd accepts the following standard
 .IR file .
 These options must appear before all other options.
 .PP
+In addition, the option
+.B -singleInstance
+is treated like an X option (it must appear before all other
+options), and it runs MrEd in single-instance mode.
+In single-instance mode, when an existing instance
+is running with the same executable name, all non-option
+arguments are treated as file names and sent to the 
+existing instance.
+.PP
 
 .SH STARTUP FILE AND EXPRESSION OPTIONS