The ingestion of plain coffee was compared in 150 duodenal ulcer patients (DU) and 100 control subjects without digestive complaints (C). The DU and C groups were registered in accordance with their daily consumption of coffee: none, 1-100 ml, 101-300 ml, 301-500 ml, and more than 500 ml. Fifty millilitres of coffee as prepared in Brazil contain around 50 mg of a caffeine, which is 2.8 times more than in an equal volume of coffee in the United States. Patients with DU stopped drinking coffee or reduced the volume significantly after symptoms started. There was a significant change in coffee intake at all volume levels except at 1-100 ml. The main reason for the reduction of coffee ingestion was the relationship observed by the patients between the consumption of coffee and dyspeptic complaints. Our results suggest a close correlation between the ulcer-like symptoms and the amount of coffee ingested by patients with duodenal ulcer.