Venoms of nine different snake species of the genus Bothrops were fractionated using fast protein liquid chromatography (FPLC). Basic proteins with phospholipase A2 and/or myotoxic activities were isolated from venoms of B. jararacussu, B. moojeni, B. neuwiedi and B. pradoi. B. jararaca venom possessed very low concentrations of these proteins, which were undetectable in venoms of B. atrox, B. alternatus, B. cotiara and B. erythromelas. Basic proteins from B. moojeni and B. pradoi venoms were isolated in pure form. All active fractions possessed a common band of 15,000 mol. wt which caused a rise in serum creatine phosphokinase levels and histopathological changes in muscle cells following i.m. injection into mice. Levels of phospholipase A2 activity were variable. The implications of the possession of varying levels of myotoxins and phospholipase A2 in these venoms are discussed.