1. Vesamicol (2-[4-phenylpiperidino] cyclohexanol) inhibits the transport of acetylcholine into synaptic vesicles in cholinergic nerve terminals. 2. Recent pharmacological studies of the effects of vesamicol on skeletal neuromuscular transmission have revealed a pattern of activity for the compound consistent with the neurochemical observation of the mechanism of action of the compound. 3. Pharmacological manipulation of vesicular acetylcholine transport has been used to investigate the recycling and mobilization of synaptic vesicles within cholinergic nerve terminals. 4. In addition to its effects on vesicular acetylcholine transport, vesamicol also possesses some sodium channel and alpha-adrenoceptor blocking activity. 5. Vesamicol clearly represents a unique tool for investigating presynaptic mechanisms in cholinergic nerve terminals.