cua

I've tried various version to no avail: (global-set-key (kbd "C-<space>") 'tempo-complete-tag) (global-set-key [C-space] 'tempo-complete-tag) I'm using CUA mode and running Emacs on Ubuntu, version: GNU Emacs 23.1.50.1 (x86_64-pc-linux-gnu, GTK+ Version 2.18.0) of 2009-09-27 on crested, modified by Debian When I run tempo-complete-tag manually it tells me it is bound to C-space but C-space still runs cua-set-mark (or if CUA is disable, set-mark-command ). How can I rebind the C-space shortcut in Emacs to a command I decide? C-h k (key) will tell you how Emacs refers to a given key (which is "C