BACKGROUND Since the discovery, several decades ago, of the infection of the gastric mucosa with Helicobacter pylori and its association with chronic antral gastritis and peptic ulcer, the treatment of ulcer illness has recently been revolutionized. METHODS In this study, the clinical effectiveness of three schemes of treatment with colloidal bismuth subcitrate (CBS) were compared. Fifty-three patients suffering from gastroduodenal peptic ulcer with Helicobacter pylori were distributed randomly into three groups. Group I (n = 17) received 240 mg CBS every 12 h for 6 weeks. Group II (n = 17) received 240 mg CBS every 12 h for 6 weeks, pus metronidazole 500 mg every 8 h plus tetracycline 500 mg every 8 h for 10 days. Group III (n = 19) received 240 mg CBS every 12 h for 6 weeks, plus metronidazole 500 mg every 8 h plus amoxicillin 750 mg every 12 h for 10 days. A duodenoscopy investigation with antrum biopsy for a morphologic study and detection of the germ was carried out by means of urease test and histological study (Warthin-Sarry and hematoxylin-eosin). RESULTS The three schemes of treatment were effective for ulcerous healing with 70.5%, 82.3%, and 78.2%, respectively, without significant differences. The highest clearing index (52.6%) was obtained in group III. CONCLUSIONS With these treatments, the Helicobacter pylori eradication was only observed in 47.3% of the patients studied.