The determination of the structure of the KcsA K+ channel from Streptomyces lividan has made it possible to investigate the function of a biological channel at the atomic level ( Doyle et al, 1998 ). Because of its structural similarity with eukaryotic K-channels, investigations of KcsA are expected to help understand a large class of biologically important channels. We are currently working on several fundamental aspect of the function of the KcsA channel such as, electrostatics, muti-ion permeation, channel gating, and inhibition by various blocking agents (see Roux and MacKinnon, 1999 ; Berneche and Roux, 2000; Roux et al., 2000; Crouzy, et al, 2001; ; Berneche and Roux, 2001).