Two colipases, named colipase I and colipase II, have been isolated from extracts of human pancreatic gland. The two proteins can be separated by ionexchange chromatography, isoelectric focusing and slab technique gel electrophoresis. The result of this study indicates that the two colipases, both of which are glycoproteins, have identical amino acid compositions. The p I values were found to be 6.1 for colipase I and 5,8 for colipase II. The different colipases have also been found in human pancreatic juice. The N-terminal amino acid was glycine for both colipase I (gland) and colipase II (juice). Only minor differences were found between the colipases isolated from gland and juice, and colipase I from gland alone was examined in detail.