One hundred and eleven specimens of dysplasia and carcinoma of gastric mucosa were studied morphometrically with automatic IBAS image analysis system. A total of 12 parameters of histologic and cellular changes were measured. The results showed that index of structural atypism, gland area, gland perimeter, gland maximum diameter, nucleus-gland ratio index and nuclear area increased in the order of intestinal metaplasia, mild dysplasia, moderate dysplasia, severe dysplasia and carcinoma. These data indicate that computer-assisted morphometry can offer objective criteria in the differential diagnosis of gastric dysplasia and carcinoma.