Add this to your .emacs: (autoload 'actionscript-mode "actionscript-mode" "Major mode for actionscript." t) (add-to-list 'auto-mode-alist '("\\.as$" . actionscript-mode)) ------------------ ; TODO Imenu (imenu-generic-expression or imenu-create-index-function) ------------------ ; Changes in 7.2 Updated comments. See https://github.com/austinhaas/actionscript-mode for info on future changes.