Neuronal voltage-activated Ca2+ channels have received consider- able attention from scientists because of the central role played by Ca2+ in the transduction of electrical activity to chemical signals. The importance of neuronal electrical activity resulting in a rise in intra- cellular Ca2+ is highlighted at the presynaptic nerve terminal. Depo- larization of the presynaptic nerve terminal results in influx of Ca2+ through voltage-activated Ca2+ channels. This Ca2+ influx contributes to the depolarization, but more importantly, the increase in intra- cellular Ca2+ activates biochemical events culminating in vesicular release of neurotransmitter. Electrophysiological studies on presyn- aptic nerve terminals have proved difficult because of access problems and the small size of most terminals. A number of preparations, how- ever, have been amenable to studying presynaptic Ca2+ channel activ- ity. These include: