A proteolytic enzyme from the venom of Bothrops atrox snake was isolated. It was designed as Atroxin, and three chromatography steps were used to purification: ion exchange chromatography on DEAE-Sephadex A-50 equilibrated with 0.05 M Tris HCl buffer, 1 mM CaCl2 pH 7.4, followed by gel filtration on Sephadex G-50 and Sephadex G-100, respectively, using the same buffer. The enzyme was recovered with a 7.4 folds and 11% of yield. It had a high activity on casein being 7.4 optimus pH A molecular weight was 19.9 Kd calculated by polyacrilamide gel electrophoresis, and head treatment showed that the enzyme preserves its activity in the range of 37-45°C, while it was decrease when the temperature values were higher. On the other hand, 0.133 μmoles of Ca2+ and Mg2+, and Zn2+ ions (0.266 μmoles) were activators, while EDTA (0.20 μmoles) and sodium azide (0.053 μmoles) were inhibitors. The enzymatic activity was not affected by glicerol (1.33 μmoles) and phenyl methyl sulphonyl fluoride (PSMF) (0.16 μmoles). In addition, iodoacetic acid (0.08 μmoles) was slight inhibitor, but 0.16 μmoles of p-tosyl-l-lysine chloromethyl ketone (TLCK) was activator. Biological assays on mice showed that atroxin produced hemorrhagic and necrosis after 24 h of injection, which was increased by 5 mM calcium chloride.