OUTLINE: The trial will have 2 patient groups. Patients not in remission are assigned to group 1, while patients in remission are assigned to group 2. Then, groups are divided into 2 treatment arms. Patients failing fludarabine therapy receive cytarabine (Ara-C) IV over 2 hours on days -7, -6, -5, -4 and -3. Beginning 4 hours before the first dose of Ara-C, patients receive cladribine (2-chlorodeoxyadenosine; 2-CdA) by continuous infusion for 5 days. Patients without prior fludarabine therapy receive fludarabine IV over 30 minutes daily on days -6, -5, -4 and -3. Ara-C IV begins 4 hours after the beginning of the fludarabine infusion and continues for 4 hours. Idarubicin IV is given on days -6, -5 and -4. Donors receive filgrastim SC every 12 hours for 2 days prior to stem cell collection. Cells are infused on day 0. For GVHD prophylaxis, all patients receive cyclosporine via continuous IV infusion. Oral cyclosporine is administered once patients tolerate oral feeding and continued for 6 months postinfusion. Then, the dose of cyclosporine is tapered 10% weekly until discontinued. Methylprednisolone begins 5 days after infusion and is gradually tapered.