An 8-year old girl was diagnosed as having idiopathic thrombocytopenic purpura which later became refractory to steroids, splenectomy, and immunosuppressive therapy. While she was being treated for pneumococcal meningitis, 7 1/2 years later, she was found to have Philadelphia-chromosome-positive chronic myelocytic leukemia. She died 2 1/2 years after the diagnosis of leukemia. The association of autoimmune disorders and hematologic malignancies has been well-recognized. To our knowledge, there has been no previous report of chronic idiopathic thrombocytopenic purpura preceding the development of chronic myelocytic leukemia in the literature.