Abstract Chemical, physical and biochemical properties of Crotalus durissus cumanensis venom were investigated. Most of the chemical and physical characteristics conform with the general pattern for Crotalidae, but there are noticeable variations in relation to the degree of activities of the ten types of enzymes assayed. Immunoelectrophoresis of the venom showed eleven precipitation lines of which, six migrated to the anode, four to the cathode and one remained at the point of application. The lethality of the venom assayed by i.v. and i.p. injection in white mice gave ld 50 values of 666 and 1143 μg per kg, respectively. The symptomatology suggest the presence of crotamine in this venom.