The insulin-secreting pancreatic beta cell is electrically excitable and changes in the membrane potential play an important role in coupling the metabolism of glucose (and other nutrient secretagogues) to the discharge of the insulin-containing granule. The application of the patch-clamp technique, which permits the recordings of the minute currents associated with the opening of individual ion channels, to pancreatic islet cells has revolutionized our understanding of the beta cell electrophysiology. Here we review some of the recent progress in the field. The properties of functionally important ion channels are described and their possible roles are discussed.