A 40-year-old woman, who had suffered from AML (M1) in 1983, developed ovarian cancer (stage IIIc) in December 1996 after long-term remission. She underwent surgical resection of the cancer, 10 courses of standard chemotherapy and tandem PBSCT (total dose: CBDCA 6,750 mg, CDDP 200 mg, CPA 16,000 mg, THP-ADR 450 mg). After receiving the last course of chemotherapy in June 1998, she was referred to our hospital in September 1998 because of pancytopenia. Laboratory findings showed pancytopenia with 34% leukemic cells, which were positive for alpha NBE and negative for POX and CAE. Surface-marker analysis of the leukemic cells showed positivity for CD11c, CD33, CD56, and DR, and chromosome analysis revealed 47, XX, +8. The patient was diagnosed as having AML (M5a), and received induction therapy consisting of IDR and Ara-C, which led to complete remission. As she had not received etoposide, this case was thought to have been therapy-related leukemia due to the platinum agents used for treating the ovarian cancer.