A total of 23 patients with high-risk acute myelogenous leukemia (AML) at diagnosis (2 patients), relapsing AML (14) or resistant AML (6) were treated with 25 micrograms/kg i.v. plicamycin every other day for 3 weeks and 500-4,000 mg hydroxyurea per day p. o. according to the WBC count. Aplasia was observed in only two patients. Severe extrahematologic toxicity included sepsis (four cases), vomiting (four patients), toxic hepatitis (three cases), and fibrinopenia (one patient). No partial or complete responses were observed. The 95% confidence interval limit of the overall response rate (CR + PR) was 0-14%.