Cranberry constituents are known to exert anti-adhesion activity on H. pylori in vitro. To determine their possible additive effect to triple therapy with omeprazole, amoxicillin and clarithromycin (OAC), a double-blind randomized clinical study was carried out. One-hundred-seventy-seven patients with H. pylori infection treated with OAC for 1 week were randomly allocated to receive 250 mL of either cranberry juice (cranberry-OAC, n = 89) or placebo beverage (placebo-OAC, n = 88) twice daily and only cranberry juice or placebo beverage for the next 2 weeks. Treatment outcome was determined with the(13)C urea breath test ((13)C-UBT). An additional control group consisted of patients referred to the same center during the same period who were treated with OAC alone for 1 week (non-placebo-OAC, n = 712). Overall, the rate of H. pylori eradication ((13)C-UBT 3.5) was 82.5%, with no statistically significant difference among the three arms. Analysis by gender revealed that for female subjects, the eradication rate was higher in the cranberry-OAC arm (n = 42, 95.2%) than in the placebo-OAC arm (n = 53, 86.8%) and significantly higher than in the non-placebo-OAC group (n = 425, 80%; p = 0.03). For males, the rate was nonsignificantly lower in the cranberry-OAC arm (n = 35, 73.9%) than in the placebo-OAC arm (n = 45, 80.0%) and non-placebo-OAC group (n = 287, 85.0%). These results suggest that the addition of cranberry to triple therapy improves the rate of H. pylori eradication in females.