A 55-year-old woman developed a secondary leukemia following 1-year treatment of Hodgkin's disease. She was admitted to our hospital because of the celiac lymphadenopathy. Open laparotomy was performed. Biopsy specimens of the lymph node demonstrated Reed Sternberg cells with mature lymphocytes. She was diagnosed as having Hodgkin's disease (lymphocyte predominant type). She was treated by the combination chemotherapy consisting of mitoxantrone, cyclophosphamide, vincristine and prednisolone for Hodgkin's disease in November 1986. Hodgkin's disease achieved complete remission and she was regularly followed. No abnormal findings were observed in the peripheral blood and bone marrow. But thrombocytopenia and the blastoid cells appeared in the peripheral blood in February 1988. The bone marrow specimen was hypercellular and occupied by 90% of blastoid cells that were positive for peroxidase staining. She was diagnosed as having AML from the bone marrow aspiration and biopsy specimens. She did not respond to several chemotherapy regimens and now she is treated by low dose Ara C.