The overlapping fragments of the chromosomal DNA from black widow spider Latrodectus mactans carrying genes for high-molecular-mass protein neurotoxins, α- and δ-latroinsectotoxins (α-LIT and δ-LIT) and α-latrotoxin (α-LTX), were PCR-amplified and cloned. Restriction analysis of the PCR products showed that the distribution and sizes of the restriction fragments coincided with those deduced from the earlier sequencing of cDNAs of the corresponding genes. It thus followed that the α-LIT and δ-LIT genes are intronless. Along with our data on the structure of the α-latrocrustotoxin (α-LCT), this implies that the lack of introns is a common feature of the black widow spider genes encoding high molecular mass neurotoxins.