High-dose cytosine arabinoside ( HDARAC ) and 4'-(9 acridinylamino) methane sulfon -m-anisidine (m-AMSA) was administered as induction therapy to 40 patients with relapsed or refractory acute nonlymphocytic leukemia (ANLL) with the following results: 28 patients (70%) achieved complete remission, one patient achieved a partial remission; five patients died with hypoplastic bone marrows containing less than 5% blasts; four patients died with hypoplastic marrowing containing greater than 5% blasts; and three patients failed to achieve marrow aplasia and died without significant cytoreduction in percentage of blasts. Consolidation therapy was not used and maintenance therapy was given to less than 10% (three patients) of remission patients. The median duration of remission for all patients was 6.0 months and the median time for the complete remission patients exceeded eight months. This regimen has acceptable toxicity and the results are equivalent to those obtained from conventional induction therapy of de novo ANLL patients.