BACKGROUND Although the eradication of Helicobacter pylori infection benefits patients with gastric or duodenal ulcers, the value of eradicating the infection in the patients with functional dyspepsia (FD) remains controversial. AIMS To determine whether eradicating H. pylori can prevent the subsequent development of ulcers or relieve the symptoms of functional dyspepsia patients. METHODS In a double-blind, placebo-controlled trial, 161 patients infected with H. pylori who had functional dyspepsia were randomly assigned to 7 days of treatment with a lansoprazole-based triple therapy or placebo and then followed for 1 year. The main outcome measures were the development of peptic ulcers and the resolution of symptoms. RESULTS H. pylori was eradicated in 63 out of 81 patients (78%) in the treatment group and none of the 80 patients (0%) in the placebo group. During the follow-up period, two patients in the treatment group and six patients in the placebo group developed peptic ulcers at repeat endoscopy (2.5% vs. 7.5%; 95% CI: -12 to 2). The reduction in ulcer rates was statistically significant in the 'ulcer-like' sub-group (0% vs. 16.7%; 95% CI: -32 to -2), but not in the 'dysmotility-like' and 'unclassifiable' sub-groups. Regarding symptom response, the resolution rates of symptoms were similar between the treatment and placebo groups (58.0% vs. 55.0%, 95% CI: -12 to 18). Additionally, no significant differences existed in the symptom responses between the treatment and control arms in each of the dyspepsia sub-groups. CONCLUSIONS Eradicating H. pylori can prevent the subsequent development of peptic ulcers in the patients with 'ulcer-like' functional dyspepsia. However, this approach does not significantly reduce the symptoms of functional dyspepsia patients.