A twelve-year series of 375 patients with gastric carcinoma has been studied. Primary tumours were classified as intestinal type (58%) or diffuse (26%), whereas 16% were unclassifiable. The relative age and sex incidence rates of intestinal type and diffuse gastric carcinoma were estimated using the age and sex distribution of individuals in Norway as the basis for calculation. There was no difference in the rates of diffuse gastric carcinoma between the sexes. On the other hand, the rate of men with intestinal type carcinoma was more than twice as high as that of women. This difference was consistent within each age group from adolescence to senescence. The findings indicate that Laurén's two types of gastric carcinoma are aetiologically different. The rates of both types increased with age up to the 70-79 age group, whereas the rates in octogenarians tended to be lower than in septuagenarians. A comparison of our data with the data of incidence of gastric cancer in Norway indicates that some of the older patients do not come for surgery.