Chronic immune thrombocytopenic purpura (ITP) is an autoimmune disorder characterized by increased platelet clearance because of antiplatelet antibodies. It was recently reported that the balance of T helper 1 (Th1) and T helper 2 (Th2) subsets has been implicated in the regulation of many immune responses. In this study, the intracellular interleukin-4 and interferon-gamma production in CD4+ T-lymphocytes activated by phorbol 12-myristate 13-acetate and ionomycin was assessed via flow cytometry in order to determine the clinical significance of the Th1/Th2 ratio in 42 patients with ITP. The study cohort included 28 untreated patients, seven postprednisolone therapy patients and seven postsplenectomy patients. The mean level of the Th1/Th2 ratio in the untreated group was 36.9 (95% CI 25.8-47.9), and significantly higher than in the control group (mean 12.8, 95% CI 9.5-16.1). The mean levels of the Th1/Th2 ratio in the postprednisolone therapy and postsplenectomy groups were 20.5 (95% CI 8.4-32.6) and 16.4 (95% CI 3.1-29.7), respectively, but were no significant differences as compared with control subjects. When untreated patients were divided into two subgroups by Th1/Th2 ratio, the mean level of platelet associated IgG in the high Th1/Th2 subgroup (higher than upper limit of control group) tended to be higher than in the normal Th1/Th2 subgroup. In conclusion, the high Th1/Th2 ratio was closely related to the etiology and disease status of chronic ITP.