An unexpected variety of different types of Ca2+ channels have been identified using molecular cloning and selective Ca2+ channel toxins. A main focus of current research in this field is to characterize these different channel types and the molecular mechanisms by which Ca2+ channels perform their basic activities of gating, selectivity and modulation. Recent advances demonstrate the roles of different types of Ca2+ channels in muscle and nerve, and provide hints about the structures involved in selectivity and gating.