The hyaluronidase from Bothrops atrox venom was purified and characterized. The effect of monovalent and divalent ions on their catalytic activity was studied, showing that the magnesium ion (150 mM) increases de activity in 40%, while glycine inhibits it by 44 %. The enzyme lacks toxic activity, when administered in albino mice in toxicity tests, but increases the hemorrhagic action of the total venom on the skin of these animals. The polyvalent botropic antivenom, was able to recognize components of the total venom of B. atrox, as well as the purified enzyme, in immunodiffusion assays. The cDNA coding for hyaluronidase from the venom of B. atrox was obtained from mRNA extracted of the fresh venom, and sequenced. The analysis of the cDNA, of 2020 bp, shows that it contains an ORF of 1350 bp that codes for a pre-enzyme of 449 amino acids, which probably is processing resulting in a matur...