Helicobacter pylori is present in up to 87% of patients with nonulcer dyspepsia. This study assessed the effect of eradicating Helicobacter pylori infection on the symptoms of nonulcer dyspepsia at four weeks and one year after treatment. Dyspepsia was assessed on the frequency and severity of six symptoms [epigastric pain (night and day), nausea and vomiting, upper abdominal discomfort, and regurgitation] where each symptom was scored from 0 to 4. Helicobacter pylori status was assessed before treatment and four weeks after treatment with histology and microbiology, and at one year with a carbon-13 urea breath test. Eighty-three patients (23 males, 60 females; mean age 56.3 years; mean symptom duration 3.6 months) with nonulcer dyspepsia and Helicobacter pylori infection entered the study. Seventy-five were available at one year follow-up. Four weeks after treatment, the mean symptom score improved in those with eradication (6.95-2.3, P = 0.01, N = 41) or persistent infection (6.69-3.0, P = 0.015, N = 42). At one year, those with persistent Helicobacter pylori infection (N = 38, score 5.24) had a higher score than those remaining clear of infection (N = 24, score 1.4, P < 0.0001) and those with reinfection (N = 13, score 2.2, P < 0.0001). In addition, persistent Helicobacter pylori infection was associated with more additional treatments than those with eradication (34/38 versus 4/37, P < 0.001). These results suggest that Helicobacter pylori plays an important role in the symptoms of nonulcer dyspepsia.