In a prospective randomized trial, the pending question was addressed whether Cytosine arabinoside (Ara-C) should be applied at high or intermediate dose to patients with relapsed or refractory acute myeloid leukemia. Based upon the previously established regimen of the sequential application of Ara-C and Mitoxantrone (S-HAM) patients below 60 years of age were randomized to receive Ara-C at either 3.0 g/m2 vs 1.0 g/m2 per dose while older patients were randomly assigned to either 1.0 g/m2 or 0.5 g/m2 Ara-C. At the present early stage 51 patients have entered the study and 37 are currently evaluable for response and toxicity. Complete remissions were achieved in 14 of 28 patients below 60 years of age and in 3 of 8 older cases. Predominant side effects consisted of nausea and vomiting, diarrhea and stomatitis. Further recruitment of patients and longer follow-up is required for the assessment of the various treatment arms.