In this study, the efficacy and tolerability of two different therapeutic schedules in eradicating Helicobacter pylori and healing duodenal ulcer were evaluated. The study included 60 patients with duodenal ulcer and Helicobacter pylori infection. They were randomly allocated to either of two groups: group 1 (N = 30) received omeprazole 20 mg for 28 days, amoxicillin 3 x 500 mg for 7 days and metronidazole 3 x 500 mg for 5 days, and group 2 (N = 30) received omeprazole 20 mg for 28 days, ACA (amoxicillin 500 mg plus clavulanic acid 125 mg) 3 x 625 mg for 7 days and metronidazole 3 x 500 mg for 5 days. Endoscopic examination, bioptic urease test and histologic examination were performed before, and 30 and 90 days after the treatment. Endoscopic examination was also performed one month after the beginning of the treatment, when healing of duodenal ulcer was observed in 90% (27/30) of the group 1 patients and in 93.3% (28/30) of the group 2 patients. The Helicobacter pylori eradication achieved in group 1 and 2 was 76.7% (23/30) and 83.3% (25/30), respectively. Side effects were present in 20% (6/30) of the group 1 patients and in 23.3% (7/30) of the group 2 patients. Side effects were mild and did not require interruption of the treatment. A higher rate of eradication was achieved in group 2 than in group 1, but the difference was not statistically significant.