Mitoxantrone (MIT, 12 mg/m2, i.v. 5 days) and intermediate-dose cytosine arabinoside (IDAC 1 g/m2/12 h, i.v. 3 days) was given to 43 patients with poor-risk acute leukemias (AL). Moderate or severe toxicity was infrequent. The proportion of complete remissions (CR) in the main patient categories was as follows: 15/18 (85 per cent) in acute myeloid leukemia (AML) in the first relapse, 2/6 in ALL in the first relapse, 0/2 in AML in relapse after bone marrow transplantation (BMT), 2/7 in AML refractory to first-line treatment (REF-AL), and 1/6 in postmyelodysplastic (PMD-AL) plus secondary AL (S-AL). The mortality rate during induction was 23 per cent. Median duration of CR was 24 weeks. The multivariate prognostic factor analysis on CR obtention showed that data concerning treatment for the first relapse and platelet count higher than the median of the series were favourable. On the contrary, PMD-AL, S-AL and REF-AL were unfavourable situations. A percentage of marrow erythroblasts superior to the median was a favourable prognostic factor for survival. Finally, the duration of CR after MIT-IDAC was directly related to the duration of previous CR. In conclusion, MIT-IDAC was highly effective to attain CR in AML in the first relapse. However, due to the poor long-term results in these patients, additional measures are recommended after CR.