A case-control study on diet and gastric cancer, carried out in selected areas of four regions of Spain (Aragon, Castile, Catalonia, and Galicia) in 1988 and 1989, included 354 cases of histologically confirmed gastric adenocarcinoma and 354 controls matched by age, sex, and area of residence. Cases and controls were selected from 15 hospitals, representing most of the hospital facilities in the study areas. Usual diet was estimated by means of a dietary history questionnaire administered by interview. An increased risk of gastric cancer was observed for high consumption of exogenous nitrosamines (odds ratio = 2.1 for the highest quartile of consumption versus the lowest; p for linear trend = 0.007), nitrites, fat, and cholesterol. However, in a multivariate regression model, the effect of fat and cholesterol disappeared. An inverse association with the risk for gastric cancer was seen for high intake of fiber, vitamin C, folate, carotene, and nitrates. High consumption of vitamin C seemed to neutralize the increased risk related to simultaneous consumption of nitrosamines. For histologic type, the authors found no meaningful differences in the effect of most of the nutrients between intestinal and diffuse cancers. Their findings are consistent with previously reported results about the protective effect of fruit and vegetables and the increased risk associated with foods that are important sources of nitrites and preformed nitrosamines.