As known some natural neurotoxins can effectively influence the secretion process of a neurotransmitter from the nerve ending. Among such neurotoxins particular interest is presented by the toxic components of the black widow spider Latrodectus mactans tre-decimguttatus. Latrodectus toxins affect on all synapse types of various classes of animals, causing a massive release of a transmitter from the nerve terminal (Longenecker et al., 1970; Frontali, 1972; Grasso et al., 1979). α-Latrotoxin (α-LTX) is major toxic component of the black widow spider venom selectively toxic to vertebrates. The toxin can induce the transmitter release from nerve terminals and PC cells both in calcium and calcium-free medium (Grasso, 1988). The cDNA encoding the putative α-LTX precursor contains the 4203 base-pair open reading frame corresponding to the 156,855 Da protein composed of 1401 amino acid residues (Kiyatkin et al., 1990). But the molecular mass of the toxin deduced from the cDNA considerably differs from that determined for α-LTX by means of SDS gel electrophoresis (Ushkarev & Grishin, 1986) assuming possible processing in the C-terminal part of the polypeptide chain during its maturation. The size of the α-LTX molecule as well as its multifunctional properties might testify to the existence of several functional domains in the toxin structure. The paper summarizes the experimental results, which allow us to define some functional domains of the α-LTX molecule.