The aim of our study is to evaluate the efficacy and tolerability of four different therapeutic regimens for Helicobacter pylori eradication. One-hundred and thirty-two consecutive patients suffering from either peptic ulcer or non-ulcer dyspepsia, with Helicobacter pylori infection, were allocated to one of the following 4 groups with different therapeutic regimens: A) omeprazole 20 mg bid for 14 days/amoxycillin 1000 mg bid for 14 days/tinidazole 500 mg bid for 14 days (30 patients, 13 with peptic ulcer); B) omeprazole 20 mg bid for 14 days/amoxycillin 1000 mg bid for 14 days (41 patients, 23 with peptic ulcer); C) omeprazole 20 mg bid for 14 days/azithromycin 500 mg/day for 3 days for 2 consecutive weeks (25 patients, 12 with peptic ulcer); D) omeprazole 20 mg/day for 7 days/clarithromycin 250 mg bid for 7 days/tinidazole 500 mg bid for 7 days/ (36 patients, 14 with peptic ulcer). The Helicobacter pylori status was evaluated by means of histology, culture and urease test, at entry and 8 weeks after treatment. 2 group A, B and D patients, 1 D patient didn't complete the treatment. In evaluable patients, the Helicobacter pylori eradication was obtained in 24 patients of group A (85.71%), in 24 of group B (58.98%), in 11 of group C (45.83%) and in 24 of group D (70.58%). On intention-to-treat analysis, Helicobacter pylori eradication was 80% in group A, 56.09% in group B, 44% in group D and 66.67% in group D. Sideeffects occurred in 6 patients of group A (20.68%), in 5 of group B (12.5%), in 3 group D (8.82%) and none of group C. In conclusion, triple therapy with omeprazole/clarithro-mycin/tinidazole is better for cost/benefit ratio; omeprazole/amoxycillin/tinidazole is more effective than others regimens in the Helicobacter pylori eradication, but causes more side effects; double therapy with omeprazole/azithromycin is the most tolerable and the least efficacy for Helicobacter pylori eradication.