The review is devoted to the competitive blockers of different nicotinic ac
etylcholine receptors, alpha-neurotoxins from snake venoms, and alpha-conot
oxins from marine snails of the Conidae family. The relationship between th
e structure and function of these toxins is discussed. Recent data on the m
echanism of alpha-neurotoxin and alpha-conotoxin interaction with the nicot
inic acetylcholine receptor are presented.