Helicobacter pylori (H. pylori) is currently considered the most important exogenous factor in the genesis of gastritis and peptic ulcer disease. However, the optimum regimen for the eradication of H. pylori remains unclear. The purpose of this study was to evaluate the eradication rate of H. pylori, the side effects, and the patients' compliance with regard to various drug regimens. We also analyzed factors influencing the eradication of H. pylori. One hundred and eighty patients were included and divided into four groups: 42 patients (Group I) received tripotassium dicitrato bismuthate (240 mg b.i.d.), metronidazole (250 mg t.i.d.) and amoxicillin (500 mg t.i.d.) for 14 days; 55 patients (Group 2) received omeprazole (20 mg b.i.d.) and amoxicillin (1000 mg b.i.d.) for 14 days; 36 patients (Group 3) were treated with omeprazole (20 mg b.i.d.), metronidazole (250 mg t.i.d.) and amoxicillin (500 mg t.i.d.) for 14 days; and 47 patients (Group 4) received omeprazole (20 mg q.d.) and Famoxicillin (500 mg t.i.d.) for 14 days and then tripotassium dicitrato bismuthate (240 mg b.i.d.) and nizatidine (150 mg q.d.) for 14 days. The diagnosis of H. pylori was made by histology. The eradication of H. pylori was defined both by histology (H&E and Giemsa stain) and by rapid urease test (CLO^R) showing negative for H. pylori 4 weeks after the completion of therapy. Of the 180 patients, 95 patients had non-ulcer dyspepsia, 40 patients had gastric ulcer and 45 patients had duodenal ulcer. The eradication rate of H. pylori was highest (89.3%) in Group 3, as compared with Group 1 (68.9%), Group 2 (65.4%), and Group 4 (48.9%). The eradication rate was significantly higher in Group 3 than in Groups 2 and 4 (p < 0.05). There was no significant difference in the eradication rate among clinical diagnosis, sex and age. But, in the conventional triple therapy (Group 1), the eradication rate was higher in male (78.6%) than in female (46.2%). The side effects in order, were nausea (22.1%), dizziness (19.5%), abdominal pain (11.6%) and diarrhea (97%), and there was no difference among the drug regimens. The compliance of the patients was good (more than 80% irrespective of drug regimen). On the basis of these findings, the side effects of the drugs seemed minimal, and the compliance of patients was good irrespective of the drug regimen. In conclusion, the triple therapy with omeprazole, metronidazole and amoxicillin was the most effective regimen and could be recommended for H. pylori eradication.