OBJECTIVES: I. Assess the value of idarubicin added to the standard conditioning regimen of allogeneic and autologous stem cell transplantation in patients with leukemia or myelodysplastic syndrome at high risk of relapse. II. Determine time to recovery of polymorphonuclear neutrophil leukocyte (PMN) and platelet counts in these patients. III. Evaluate the rate and type of grade 3-4 toxicity, particularly mucositis, and the number of days with fever in these patients. IV. Determine the incidence of acute and chronic graft versus host disease (GVHD) in these patients.