A phospholipase A(2)(PLA(2)) was purified from the venom of the snake Trimeresurus stejnegeri Schmidt by Sephadex G-75 gel filtration, Mono Q ion exchange chromatography and Superose-12 gel filtration with FPLC and proved to be homogeneous as shown in SDS-PAGE and IEF. Its molecular weight is around 18 000 and isoelectric point is 4.7. Amino acid composition of PLA(2) was determined. Apart from hydrolyzing phosphatidylcholine, the enzyme has a potent inhibitory effect on platelet aggregation induced by ADP or collagen with half-inhibitory concentration of 10-15 &mgr;g/ml and 50-80 &mgr;g/ml respectively.