Two phospholipase A2 isozymes have been purified from leaf-nosed viper by gel permeation chromatography followed by reverse-phase HPLC and cation-exchange FPLC. Both enzymes contain seven pairs of half-cystine, typical of group II phospholipase A2. Surprisingly large differences, affecting both N- and C-terminal regions, exist between the two isozymes purified from the same snake venom. Exchanges occur at no less than 27 of 121 positions (22%), suggesting the possible existence of two genes for phospholipase A2. The residue identity with the enzymes from other Viperidae species is also low, only 44-48%, indicating extensive variations of this protein structure at large. Functionally, the present isozymes do not possess the cationic regions ascribed to myotoxicity and anti-coagulant effects of the enzyme.