A simplified 13C-urea breath test (UBT) for detection of Helicobacter pylori (Hp) infection was evaluated in 50 patients. Following upper gastrointestinal endoscopy the patients received 100 ml of a liquid test meal with 100 mg 13C-urea. Breath samples were obtained at baseline and 30 minutes respectively. The UBT was positive (difference of 13CO2 enrichment exceeding 5%) in 33/35 patients with culture-proven Hp infection and negative in 14/15 patients in whom microbiological culture, histology and a urease test (CLO-test) were negative. We conclude that in view of its high sensitivity (94%) and specificity (93%) the UBT is useful for rapid, non-invasive diagnosis of Hp infection.