Whether the eradication of Helicobacter pylori infection can increase the platelet count in patients with immune thrombocytopenic purpura (ITP) is still a controversial issue. To provide evidence-based guidance, we performed a systematic review of the literature published in English, selecting articles reporting 15 or more total patients. We identified 25 studies including 1555 patients, of whom 696 were evaluable for the effects of H pylori eradication on platelet count. The weighted mean complete response (platelet count > or = 100 x 10(9)/L) and overall response (platelet count > or = 30 x 10(9)/L and at least doubling of the basal count) were 42.7% (95% confidence interval [CI], 31.8%-53.9%) and 50.3% (95% CI, 41.6%-59.0%), respectively. In 222 patients with a baseline platelet count less than 30 x 10(9)/L, the complete response rate was 20.1% (95% CI, 13.5%-26.7%) and the overall response rate was 35.2% (95% CI, 28.0%-42.4%). The response rate tended to be higher in countries with a high background prevalence of H pylori infection and in patients with milder degrees of thrombocytopenia. These findings suggest that the detection and eradication of H pylori infection should be considered in the work-up of patients with seemingly typical ITP.