Antibodies against the human cholesterol-binding pancreatic protease/elastase 1 (Sziegoleit, A., Linder, D., Schlüter, M., Ogawa, M., Nishibe, S. & Fujimoto, K. 1985) Eur. J. Biochem. 151, 595-599) recognize a distinct protein in the pancreas homogenate of various animal species. The CBPP/elastase 1-related porcine protease was purified and characterized. Its properties, including specificity, proved to be the same as those of the well classified porcine pancreatic protease E (Kobayashi, R., Kobayashi, Y. & Hirs, C.H.W. (1981) J. Biol. Chem. 256, 2460-2465). While the common features of all these proteins seem to be the proteolysis with elastase-like specificities (investigated for the human-, porcine-, dog- and rat-derived protein) and an isoelectric point at about pH 5 (determined for the pancreatic proteins from man, swine, rat dog and cattle), the bile salt and cholesterol-binding capacity varies significantly among the animal species. Charge shift crossed immunoelectrophoresis of the pancreatic proteins from rat, dog, cat, swine, horse, zebra, cattle and rabbit reveals that only the protein from rat pancreas binds the negatively charged bile salt sodium deoxycholate to an extent comparable to that of human CBPP/elastase 1. Thus, within the diverse elastase family, there seems to be a distinct enzyme which merits distinct classification.