In this study, in vivo effectiveness of ascorbic acid (AA), beta carotene (BC) and allicin in HP eradication were evaluated. 210 patients who are HP positive in biopsy were involved in this study. The patients randomised to seven treatment groups (each group consisting of 30 patients). The first group was given standard eradication treatment (lansaprasol 30 mg bid, clarithromycin 500 mg bid, amoxicillin 1 g bid for 14 days). Second group received AA 1000 mg/day in addition to the standard treatment. Third group received only AA 1000 mg/day for 14 days. Fourth group was treated with standard regiment plus 120 mg/day BC. Fifth group was given only BC 120 mg/day for 14 days. Sixth group was given standard regiment and allicin 4200 micrograms/day. Seventh group received only Allicin 1200 micrograms/day for 14 days. The eradication was achieved in 20 (66.6%) in group I, 15 (50%) in group II, 3 (10%) in group III, 15 (50%) in group IV, 0 (0%) in group V, 27 (90%) in group VI and 7 (23.3%) in group VII. Allicin seemed to be potentially effective agent for HP eradication but ascorbic acid, beta caroten was found to be ineffective.