Delta over baseline (DOB) values of 13C-urea breath test (UBT) have been shown to be predictive of H. pylori eradication following therapy. This was a post hoc analysis of a large, double-blind, randomized trial. Consecutive patients with a positive UBT underwent upper endoscopy. H. pylori strains were tested for clarithromycin resistance. All patients received an eradication therapy with either a standard 10-day triple therapy or a 10-day sequential regimen. The infection was considered cured when two consecutive UBTs were negative. Basal DOB values were categorized as low (<16), intermediate (16-35), or high (>35). A total of 282 patients were selected. Eradication rates did not differ between patients with high and low DOB values. No significant difference in DOB values emerged between patients infected with clarithromycin-susceptible and clarithromycin-resistant strains. Under multivariate analysis, DOB values did not influence the bacterial eradication, which was significantly affected only by the presence of clarithromycin resistance. This large analysis failed to demonstrate a role for DOB value in H. pylori eradication with either a 10-day triple or sequential therapy.