PURPOSE: Idiopathic thrombocytopenic purpura (ITP) was the most common disease of thrombocytopenic purpura in children, chronic course was shown in 10%. Splenectomy had been used in chronic thrombocytopenic purpura as classic therapy, and many therapeutic method had been tried. We define response to therapy and long-term outcome of chronic childhood idiopathic thrombocytopenic purpura. METHODS: We retrospectively analyzed 41 patients that treated and diagnosed as chronic thrombocytopenic purpura at the Department of Pediatrics, Severance Hospital between Aug. 1981 and Aug. 1999 and followed for mean 8.2 years. The mean age was 6.2 years (range from 1month to 12.3 years) and sex-ratio of male to female was 1:2. According to therapeutic methods, they were divided into splenectomy group, spleen irradiation group, azathioprine group, interferon group, high-dose oral dexamethasone group, vincristine group, intravenous gammaglobulin group, low-dose prednisone group, and low-dose prednisone with intermittent intravenous gammaglobulin group. The results were classified into complete response (CR: platelets> 100,000/mm3), partial response (PR: platelets> 50,000/mm3), no response (NR: platelets <50,000/mm3). RESULTS: The treatment response and number of patients according to therapeutic methods were as follows; splenectomy group, 12 cases (CR-9 cases, PR-1 case, NR-2 cases), spleen irradiation group, 1 case (CR), azathioprine group, 6 cases (CR-1 case, NR-5 cases), interferon group, 3 cases (CR-1 case, PR-1 case, NR-1 case), high-dose oral dexamethasone group, 4 cases (CR-2 cases, PR-1 case, NR-1 case), vincristine group, 2 cases (NR), intravenous gammaglobulin group, 35 cases (CR-5 cases, PR-5 cases, NR-25 cases), low-dose prednisone group, 5 cases (NR), and low-dose prednisone with intermittent intravenous gammaglobulin group, 30 cases (CR-7 cases, PR-3 cases, NR-20 cases). CONCLUSION: The results of therapeutic method in splenectomy group were the most highest score (12 cases: CR-9 cases, PR-1 case, NR-2 cases), high-dose oral dexamethasone group, interferon group, and low-dose prednisone with intermittent intravenous gammaglobulin group in high incidence order. Spleen irradiation was supposed to trial method of treatment before splenectomy, because the risk was lower than splenectomy, although they had 1 case.