The aims of this study were to assess the prevalence of Helicobacter pylori infection in chronic idiopathic thrombocytopenic purpura adult patients and investigate the platelet response after eradication. To minimize the confounding effect of concomitant idiopathic thrombocytopenic purpura therapies, patients were eligible for the prospective study if they had 20-100 x 10/l platelets, and no requirement for treatment for thrombocytopenia or no change of doses of ongoing medications for at 3 months before inclusion.Helicobacter pylori infection was assessed in 62 patients using a stool antigen test, and the infection was present in 52% of patients. Immunoglobulin G antibodies against the cytotoxin-associated gene A protein were detected in 53% of infected patients. All patients underwent sampling for specific platelet autoantibodies, 37.5% of H. pylori-positive and 33% of H. pylori-negative patients had detectable platelet autoantibodies. Sixteen eligible H. pylori-positive patients were submitted to the eradication therapy and followed in the prospective study. We considered 14 H. pylori-negative patients as control group. Platelet response was defined as an incremental increase above 50% from baseline platelet count. A positive response was observed in 43% patients after 6 months of follow-up. Eradicated responder and nonresponder patients were comparable for all main clinical features but not for anticytotoxin-associated gene A antibodies (83 vs. 12.5%, P = 0.026).Given the good cost-benefit ratio, we believe that all idiopathic thrombocytopenic purpura patients should be screened for H. pylori infection and eradication treatment should be considered, particularly for patients who are also found positive for anticytotoxin-associated gene A antibodies.