1. Reverse-phase HPLC and organic solvents were used to isolate small basic peptide (SBP) toxins from the venoms of Crotalus adamanteus, C. durissus terrificus, C. horridus, C. scutulatus scutulatus, C. viridis concolor, C. viridis helleri and C. viridis viridis. 2. Acid-DEP analyses indicated a high degree of toxin purity which was obtained with a single HPLC run. 3. The combined results of HPLC, immunodiffusion and electrophoresis analyses of venoms from different geographical regions indicate that the SBP toxin content in the venoms of Crotalus adamanteus, Crotalus horridus, Crotalus scutulatus and Crotalus viridis viridis may vary regionally.