In a case-control study of gastric cancer (GC) in high-risk and low-risk areas of Italy, 923 GCs were systematically categorized by one pathologist according to the Lauren classification distinguishing 2 main histologic types, intestinal (55%) and diffuse (23%). Intestinal types outnumbered diffuse types by a 3 to 1 margin in high-risk regions in the north-central part of the country, while both types occurred at nearly equal rates in low-risk areas. Intestinal types also occurred relatively more frequently at older ages and among males. Relative risks of each type of GC were evaluated in relation to dietary and other data obtained from interviews with the cancer patients and controls. The risk patterns for intestinal and diffuse types were remarkably similar. Increased risks of both types were associated with high intake of meat, salted/dried fish, seasoned cheeses and traditional soups, while decreased risks of both types were found among heavy consumers of fresh vegetables and fruits. Correspondingly similar patterns were seen with indices of nutrients, with risks of both intestinal and diffuse GC rising with animal protein intake and declining with consumption of vitamins C and E. Both types were inversely related to socio-economic status, and neither was associated with cigarette smoking. A familial history of GC was reported more frequently by patients with each type than by controls, although the highest risk was for unclassified GC, a group of poorly differentiated and medullary carcinomas accounting for 15% of all GCs in this study. The findings suggest that, despite differences in geographic and demographic patterns, the intestinal and diffuse types of GC have etiologic factors in common.