I know a lot of discussion about alt and mode_select has gone on previously and I apologize if this has been discussed before. The hardware: I'm running on a MacPro with a US aluminum keyboard and the Mac OS X keyboard set to US. What I'm noticing with the X11-2.1.0.pkg version installed is that the left alt/option key is seen by xev as the right alt/option key but software mapped to the left alt key. The right alt/option key is seen as the right alt, but software mapped to the left alt key. In Tiger's X11, the left alt was keycode 66 and the right alt was keycode 69 as I'd expect. Here is xev with the left alt: KeyPress event, serial 22, synthetic NO, window 0x600001, root 0x57, subw 0x0, time 77250, (42,123), root:(42,167), state 0x0, keycode 66 (keysym 0xff7e, Mode_switch), same_screen YES, XLookupString gives 0 bytes: XmbLookupString gives 0 bytes: XFilterEvent returns: False In Leopard with the 1.2a set of installs (installed by Jeremy's x11_update.sh script), the left alt again was keycode 66 and the right was 69 again as expected. Here is the xev output with the left alt: KeyPress event, serial 23, synthetic NO, window 0x200001, root 0x3f, subw 0x0, time 2993881147, (53,94), root:(53,138), state 0x0, keycode 66 (keysym 0xff7e, Mode_switch), same_screen YES, XLookupString gives 0 bytes: XmbLookupString gives 0 bytes: XFilterEvent returns: False In Leopard with the X11-2.1.0.pkg installed and post-reboot, things are rather different. Here is the xev output with the left alt: KeyPress event, serial 24, synthetic NO, window 0x200001, root 0x3f, subw 0x0, time 3126321031, (101,88), root:(101,132), state 0x0, keycode 69 (keysym 0xff7e, Mode_switch), same_screen YES, XKeysymToKeycode returns keycode: 66 XLookupString gives 0 bytes: XmbLookupString gives 0 bytes: XFilterEvent returns: False Here is the xev output with the right alt: KeyPress event, serial 27, synthetic NO, window 0x200001, root 0x3f, subw 0x0, time 3126373406, (52,84), root:(52,128), state 0x0, keycode 69 (keysym 0xff7e, Mode_switch), same_screen YES, XKeysymToKeycode returns keycode: 66 XLookupString gives 0 bytes: XmbLookupString gives 0 bytes: XFilterEvent returns: False So, something looks strange to me that by default the left alt/option key returns the keycode of the right alt/option key but then is mapped back to the left alt/option key. The real reason I was even looking at this was I use nedit a lot, so having Alt work is a major workflow advantage. Alt worked fine in Tiger without any modifications by me. In Leopard, Alt doesn't work without xmodmap modifications, but mode_switch does. Anyway, I'm working around my problem by mapping keycode 66 to Alt_L and keycode 69 to Alt_R with xmodmap (I lose mode_switch, but I have never used it anyway other than two weeks I was in Sweden using a borrowed computer). Merle