Phospholipases A2 (PLA2s) are enzymes responsible for inflammatory effects, edema formation, myotoxicity, neurotoxicity and other manifestations from envenoming. In this paper we report the isolation and biochemical characterization of Lmr-PLA2, the first acidic PLA2 found in Lachesis muta rhombeata venom. Furthermore, this study compared biological effects of Lmr-PLA2 and crotoxin B (CB), a PLA2 from Crotalus durissus terrificus venom. Lmr-PLA2 was isolated by molecular exclusion and reversed phase chromatography. The purified enzyme showed a molecular mass of 13,975 Da, pI of 5.46 and its partial amino acid sequence showed a high identity with PLA2s already described in the literature. In addition, this enzyme possesses the residue D49 in its amino acid sequence, indicating that it is a catalytically active PLA2. Lmr-PLA2 presented high phospholipase activity and was able to inhibit platelet aggregation. Studies of biochemical characterization of new PLA2s, as Lmr-PLA2, are relevant since they help to clarify the structure-function relationship of this important class of toxins.