We have investigated the relation between alcohol, tobacco and dietary habits and risk of adenocarcinoma of the small intestine using data from 2 hospital-based case-control studies on intestinal cancers conducted in 6 Italian centres between 1985 and 1996. Cases were 23 patients below age 75 years with adenocarcinoma of the small intestine. Controls were 230 patients admitted to hospital for a wide spectrum of acute, non-neoplastic, non-digestive tract diseases, matched to cases on sex, age, study and centre. Odds ratios (ORs) were estimated using conditional logistic regression. Alcohol and tobacco consumption did not increase the risk of adenocarcinoma of the small intestine. The risk appeared to be directly related to intake of bread, pasta or rice (OR = 3.8), sugar (OR = 2.9) and red meat (OR = 4.6), and inversely to coffee (OR = 0.4), fish (OR = 0.3), vegetables (OR = 0.3) and fruit (OR = 0.6). Our results suggest that dietary correlates of adenocarcinoma of the small intestine are similar to those of colon cancer and at least of the same magnitude. While the present data are inconsistent with a major effect of tobacco or alcohol, a moderate association between these factors and small bowel cancer may have been obscured by the play of chance.