binding alt key to meta on macosx

[Daan Hoogland probably]

H,

I'm amongst more running emacs 21.2.1 on moc os x 10.3.2 under X11 1.0 
- XFree86 4.3.0. I am tryng to use the alt-key as meta prefix, but in 
other applications it is giving me french, brazilian, dutch or unicode 
characters. Does anyone know of a way to get around this?

thanks,