diff --git a/doc/emacs/ChangeLog b/doc/emacs/ChangeLog
index 28bebb5afb7..321e04d5a0a 100644
--- a/doc/emacs/ChangeLog
+++ b/doc/emacs/ChangeLog
@@ -1,3 +1,8 @@
+2008-11-29  Martin Rudalics  <rudalics@gmx.at>
+
+	* windows.texi (Pop Up Window): Mention split-height-threshold
+	and split-width-threshold.
+
 2008-11-28  Adrian Robert  <Adrian.B.Robert@gmail.com>
 
 	* macos.texi: Change references to "Mac" to "Mac / GNUstep".
diff --git a/doc/emacs/windows.texi b/doc/emacs/windows.texi
index 509ee53e234..23715dcfe2a 100644
--- a/doc/emacs/windows.texi
+++ b/doc/emacs/windows.texi
@@ -224,6 +224,14 @@ window.  This runs @code{find-file-read-only-other-window}.
 @xref{Visiting}.
 @end table
 
+@vindex split-height-threshold
+@vindex split-width-threshold
+  By default, these commands split the window vertically when there is
+only one.  You can customize the variables @code{split-height-threshold}
+and @code{split-width-threshold} to split the window horizontally
+instead.
+
+
 @node Force Same Window
 @section Forcing Display in the Same Window