This study compared the phospholipases A2 (PLA2S) present in four commercially available venoms of Russell's viper subspecies by HPLC fractionation and partial sequence analysis. A potent heterodimeric PLA2 neurotoxin (designated a Russtoxin) was found in the venoms of all Russell's vipers except Daboia russelli (Sri Lanka and South India). The venom PLA2S of D. r. russelli (southern India) used in a previous study appear to be the same as those of D. r. pulchella (Sri Lanka), while the venom PLA2S of D. r. russelli (Pakistan) and D. r. siamensis (Burma and Thailand) resemble those of D. r. formosensis (Taiwan). This study provides evidence for the presence of two types of Russell's viper. Daboia russelli formosensis (Taiwan). D. r. siamensis (Thailand and Burma) and D. r. russelli (Pakistan) represent one type whose venom contains PLA2S having an Asn residue at the N-terminus, while D. r. pulchella (South India and Sri Lanka) represents the other type, whose venom contains PLA2S with a N-terminal residue Ser.