In an international multi-centre study of diet and precancerous lesions of the stomach, 24 h urine samples were analysed from 133 sets of patients with intestinal metaplasia (IM) and their matched controls from the UK, 14 sets of cases and controls from Portugal and 22 sets from Poland. In addition, urine aliquots (but not 24 h volumes) were available from 12 matched sets from Greece and 19 from Croatia. There was no difference between cases and controls in the daily urinary excretion (as a measure of daily intake) of sodium or nitrate but the potassium output by patients with IM was significantly lower than that of the controls in the UK and Portugal, and the ratio Na/K was higher in patients with IM than in controls in the UK and Portugal, but not in Poland, Greece or Croatia. Gastric juice samples were analysed from 133 sets of IM patients and endoscoped controls from the UK and 22 sets from Croatia. When compared with the endoscoped controls, IM patients from both countries had a significantly higher proportion of gastric juice samples containing bacteria and nitrite and with a pH > 6. The results are discussed in relation to current hypotheses on gastric carcinogenesis.