In this regular issue of Reviews of Physiology the first contribution by Warth and Bleich is on K+ Channels and Colonic Function, the second by Offermanns on Mammalian G-Protein Function in vivo: New Insights Through Altered Expression, and the third contribution by Tenenholz et al. (including one editor of the series) on Structural Determinants of Scorpion Toxin Affinity: The Charybdotoxin (alpha-KTX) Family of K+-channel Blocking Peptides.