This prospective, single blind, randomized study was designed to compare the efficacy and tolerance of two therapeutic schedules for eradication of H. pylori in patients with duodenal ulcer. Patients were randomized into two groups. Group 1 (n = 25) was treated with omeprazole 20 mg each morning for 28 days, azithromycin 500 mg/day for 5 days and metronidazole 3 x 500 mg/day for 5 days. Group 2 (n = 25) was treated with omeprazole 20 mg/day for 28 days and azithromycin 500 mg/day for 5 days. H. pylori status was determined by rapid urease test and histology before and 1, 6 and 12 months after the therapy. After 4 weeks of treatment ulcers healed in 96% (24/25) of patients in the first group and in 92% (23/25) of patients in the second group. One and 12 months after the treatment, eradication of Helicobacter pylori was achieved in 72% (18/25) of patients in the first group and in 64% (16/25) of patients in the second group. In 12 months after the treatment ulcer recurred in 43.7% (7/16) of patients in whom H. pylori was not eradicated and in 2.9% (1/34) of patients with eradicated H. pylori. The side effects were minor and/or transitory and did not require discontinuation of the treatment.