Snake venom proteases are interesting tools for studying coagulation reactions. Venoms contain more than 20 different compounds, mainly proteins and polypeptides. Some snake venoms have very specific effects on various biological functions, including blood clotting, regulation of blood pressure, transmission of nerve or muscle impulses. They were developed for use as diagnostic tools. Plasma coagulation factors are usually inactive and require proteolytic activation as a first step towards a chronometric or colorimetric assay. It is often advantageous to use specific enzymes from snake venoms to activate coagulation factors rather than using physiological activators. In contrast to other activators, many snake venom enzymes are not dependent on cofactors, phospholipids, or calcium ions.