Three pooled and 20 individual venom samples of Crotalus viridis lutosus from different localities in Utah and Arizona were screened and fractionated with HPLC-anion exchange. 2. Pooled venom samples and fractions were tested for hemorrhagic, collagenase, and phospholipase activities, and reactivity to a monoclonal antibody against a hemorrhagin from C. atrox venom (CA-P-8) using ELISA. 3. The 20 individual samples were organized into four groups based on their HPLC profiles. 4. ELISA results and specific hemorrhagic activity of the venom samples displayed a variation in latitidinal distribution although from the same species.