We investigated the prevalence of Helicobacter pylori infection and the effect of eradication therapy in patients with idiopathic thrombocytopenic purpura (ITP). H. pylori infection was found in 9 of 11 patients (81.8%). H. pylori eradication was obtained in all patients and significant platelet recovery was found in 5 of 9 patients (55.6%). One patient required re-eradication therapy because the urea breath test remained positive after the first therapy. After complete eradication, long time remission was obtained. The results suggested that the platelet count might be correlated closely with the amount of H. pylori in some patients with H. pylori positive ITP.