A diversity of voltage-gated K+ channels has been identified which participates in the regulation of membrane excitability and neural plasticity. After decades of intensive molecular, genetic, pharmacological and electrophysiological studies, the structure and function of K+ channels have been elucidated in great detail. In particular, impressive progress has been made in recent years from studies in Drosophila and the Xenopus oocyte expression system. This review will focus on the variety and physiological functions of K+ channels found in Drosophila. Also discussed is the possible role of coassembly of different combinations of channel subunits in the generation of K+ channel diversity. Various lines of evidence from in situ experiments in Drosophila and heterologous channel expression in Xenopus oocytes will be reviewed.