Although there have been recent reports of mucin-producing tumor of the pancreas, there has been no thorough clinicopathological analysis of a large number of cases. Two hundred forty four cases of mucin-producing tumor of the pancreas from Japanese, European and American reports, together with 15 cases of our own, were analyzed clinicopathologically. Mucin-producing tumor of the pancreas was found in 177 males and 82 females (M:F = 2.2:1). The mean age was 65.5 years. Jaundice, diabetes mellitus and a past history of pancreatitis were found in 15%-19% of the cases. The tumor was most frequently (62%) found in the head of the pancreas. Pathologically, hyperplasia or adenoma was found in 58 cases, and adenocarcinoma in 160 cases. Five-year-survival rate by the Kaplan-Meier method was 82.6% in all of the cases and postoperative survival curve was much better in cases with this type of carcinoma than in cases with ordinary pancreatic duct cell carcinoma (5-year-survival rate: 82.6% vs 17.3%). Serum tumor markers such as CEA or CA 19-9 were not effective in differentiating between benign and malignant, or in determining the degree of cancerous spread, while cytology of the pancreatic juice and biopsy of the tumor could contribute to the diagnosis. Mucin-producing tumor has unique clinicopathological characteristics, such as the dilated main pancreatic duct or branches, dilatation of the orifice of the papilla of Vater, or good prognosis. Since a diagnosis for benign or malignant is very difficult in some cases, methods for distinguishing benign from malignant lesions or for determining cancerous spread, such as molecular biological techniques, should be established.