Human spasmolytic polypeptide (hSP) is a member of the trefoil peptide group, thought to be involved in mucin production and cell growth. It has been reported that hSP protein is expressed in digestive cancers but not in normal pancreas. The expression of hSP in pancreatic neoplasms has not been investigated in detail. The immunohistochemical expression of hSP protein was investigated in pancreatic carcinomas, ampullary carcinomas, mucin-producing tumors, serous cystadenomas and islet cell tumors of the pancreas. hSP was expressed in 23% of pancreatic duct cell carcinomas, and hSP protein was more frequently detected in cases of early-stage or histologically low-grade duct cell carcinomas than in cases of late-stage or histologically high-grade carcinomas. Patients with hSP protein expression showed a better prognosis than did those with negative hSP expression. hSP expression was detected in 92% of mucin-producing tumors, but was not detected in serous cystadenoma or islet cell tumors. Immunohistochemical hSP expression is related to differentiation and a better prognosis in pancreatic duct cell carcinomas. Furthermore, hSP protein is related to the pathogenesis and clinical characteristics of mucin-producing tumors of the pancreas.