Twenty two patients with acute relapsed leukemia (AML 20, ALL 2) were treated with 5-aza-2'-deoxycytidine (DAC) and either m-amsacrine or idarubicin. DAC was administered as a 6-h infusion, every 12 h for 6 days in combination with either m-amsacrine (120 mg/m2) as a 1-h infusion on days 6 and 7 (n = 19) or idarubicin (12 mg/m2) as a 15-min infusion on days 5, 6 and 7 (n = 3). Thirteen patients (59%) achieved a complete remission. The treatment was complicated by nausea, vomiting, diarrhoea with signs of peritonitis (n = 9), weight loss (n = 7), cerebellar or cerebral toxicity (n = 2), gastrointestinal bleeding (n = 3), liver toxicity (n = 2) and prolonged myelosuppression. Median duration of remission was 4 months (range 1-30). The preliminary data show that DAC is an anti-leukemic agent, comparable to high dose Ara-C with comparable severe toxicity.