SUMMARY The prevalence, distribution, and clinical associations of pancreatic ductal mucinous hyperplasia were studied in 102 non-malignant pancreases. Ductal mucinous hyperplasia was found in over 60% of specimens and was frequently associated with increased fibrosisoccasionally resembling pancreatitis. Significantly more ductal mucinous hyperplasia was found in pancreas from patients who were receiving corticosteroid treatment. Neither a history of hypercalcaemia in the three months before death, diabetes mellitus, alcoholism, tobacco smoking, nor the presence of gall stones was associated with an increase in ductal mucinous hyperplasia. The age of maximum prevalence, and the distribution of ductal mucinous hyperplasia in the pancreas were similar to those of pancreatic carcinoma. These similarities may be because both ductal mucinous hyperplasia and pancreatic carcinoma are proliferative responses, rather than because ductal mucinous hyperplasia is a precursor of pancreatic carcinoma.