A multidisciplinary revision of snake venom includes its chemical, pharmacological and toxicological aspects. In the first part, the chemical composition of venoms, and local effects, with special atenttion to the venom of Lachesis muta muta snake are revisited. The acute toxic effects, citotoxicity, miotoxicity and the chemical basis for the production of edema, hemorrhagic and myonecrotic effects are discussed. KEYWORDS: SNAKE VENOM, CHEMISTRY, PHARMACOLOGY, ACUTE TOXICITY, CITOTOXICITY, HAEMORHAGE, MYONECROSIS, OEDEMA