Envenoming by Bothrops snakes is the most serious type of envenoming from the medical and economic point of view in Central America. Bothrops asper is responsible for 90% of the snakebites registered in Panamá every year. Despite its medical and economic relevance, only the venom of Costa Rican and Guatemalan populations of this species has been studied to some detail, and there is very little information on intraspecies variability in venom composition and toxicity. In this study the crude venom of B. asper from Panamá was characterized and its pharmacological and biochemistry activities were investigated with standard laboratory assays. Furthermore, we described the isolation, functional and structural characterization of four basic phospholipases A2, namely MTX-I, MTX-II, MTX-III, MTX-IV, and a new acid phospholipase A2 called Basp-I-PLA2. The proteins were isolated from the crude venom by a combination of two chromatographic steps, using ion-exchange chromatography on CM-Sepharose (0.05 M NH4HCO3 pH 8.1 buffer), and hydrophobic chromatography on Phenyl-Sepharose (0.05 M Tris-HCl pH 7.4), followed by concentration gradient from 4 to 0 M NaCl at 25°C in the same buffer. Analyses of phospholipids hydrolyzed by these enzymes have shown that all phospholipases belong to type A2. The acidic isoform demonstrated more catalytic activity than basic PLA2s. This enzyme was more active on substrates such as phosphotidylcholine and phosphatidylglycerol.(AU)