Subclinical morphologic changes in the pancreas detected by screening ultrasonography of 130,951 subjects were analyzed in relation to their incidence and background factors. Main pancreatic duct (MPD) dilatation, cystic lesion, and calcification were found in 644 (0.49%), 271 (0.21%) and 65 (0.05%) patients, respectively. The incidence of MPD dilatation and calcification was significantly higher in men (p < 0.0001), whereas cystic lesion was significantly more frequent in women (p < 0.01). Age-dependent increase in the incidence of MPD dilatation and cystic lesion was observed in both sexes whereas that of calcification was observed only in men. Further detailed examinations for 312 randomly selected patients with these findings revealed that 97% of MPD dilatation, 95% of cystic lesion, and 86% of calcification were correctly identified by ultrasonography. Finally, 18 (5.8%) patients with chronic pancreatitis, 16 (5.1%) with neoplastic cysts, 3 with mucin-producing tumors, and 3 with carcinomas (0.96%, respectively) were detected. On the other hand, in 84.0% of MPD dilatation, 87.4% of cystic lesion, and 50.0% of calcification, we could not attribute their etiology to any known pancreatic disease. It is indicated that aging and gender are major clinically related factors of these changes.