how to control console's resolution?

[Try KDE <trykde@rogers.com>]

In debian v3, the virtual console's resolution is deeper than 80*25, 
it's like 43 lines or something (i cannot remember, and i'm typing from 
another box now). My question  is, where is this controlled? and how to 
change it back to 80*25 if I want to ?

Thanks,
-tk