The effectiveness and toxicities of high-dose cytosine arabinoside with L-asparaginase (HiDAC-ASNase) were evaluated in 41 patients with "poor risk" acute nonlymphocytic leukemia (ANLL). Twenty-four patients had either refractory or relapsed primary ANLL, and 17 had ANLL secondary to prior cytotoxic chemotherapy or an underlying hematologic disorder. The overall complete remission (CR) rate was 37%. The CR rates for primary and secondary ANLL were almost identical. Furthermore, advanced age alone did not adversely influence the CR rate. The median CR duration was 302 days with no differences between primary and secondary ANLL. The induction death rate was 24%. Predictors for induction deaths included poor initial performance status, fever at the time of presentation, low cholesterol and/or albumin, and an initial bone marrow aspirate with greater than 50% blasts. These data indicate that HiDAC-ASNase is a moderately effective regimen for patients with poor prognosis ANLL including secondary ANLL.