Nonmyeloablative allogeneic hematopoietic stem cell transplantation (HSCT) is a transplantation approach that enables patients with comorbid conditions to undergo allogeneic HSCT. We investigated the outcome of patients with reduced renal function as a single comorbidity before HSCT. Thirteen patients with a glomerular filtration rate (GFR) of <60 mL/min/1.73 m2 were matched on sex, age, and type of transplant to 26 controls with normal renal function. All patients received a nonmyeloablative HSCT with fludarabine and/or total body irradiation conditioning (TBI). Graft-versus-host disease (GVHD) prophylaxis consisted of mycophenolate mofetil and cyclosporine. Data on renal function, cyclosporine dose, cyclosporine trough levels, hypertension, and GVHD were collected. Of the 13 patients with impaired renal function, 7 patients (54%) improved or stabilized to a GFR>or=60 mL/min/1.73 m2 at last follow-up. Four patients (31%) developed chronic kidney disease stage 3 (GFR <60 mL/min/1.73 m2) compared to 3 patients (12%) in the control group (P=.039). There was no difference in survival between cases and controls. Furthermore, there were no differences in complications after HSCT, and cyclosporine dose and trough levels were similar between cases and controls. Nonmyeloablative HSCT can be safely offered to patients with mildly reduced renal function. Cyclosporine can be administered at the same dose as patients without renal dysfunction, as long as cyclosporine trough levels and creatinine are monitored and dose adjustments are made if necessary.