Clone pHICE0.9 was selected from human insulinoma cDNA library by immunoscreening with antibodies against total human insulinoma proteins. This clone contains a 0.9 kb cDNA insert and expresses a fusion protein with beta-galactosidase. Nucleotide sequences of 5'- and 3'-terminal regions of this cDNA insert show that clone pHICE0.9 expresses a protein which is identical to the C-terminal fragment (amino acids 483 to 745) of human pancreatic cholesterol esterase and Homo sapiens bile-acid-salt-stimulated lipase from milk. It is concluded that the protein fragment contains the antigenic determinant of human cholesterol esterase/lipase, and can be used for lipase determination in blood.