Using a non-myeloablative, immunosuppressive, fludarabine-based conditioning regimen, we performed allogeneic peripheral blood stem cell transplants totally on an outpatient basis in four patients (two with chronic myelogenous leukemia, one with acute myelogenous leukemia and one with thalassemia major). The median granulocyte recovery time to 0.5 x 109/l was 10 days and the lowest absolute neutrophil count was 0.064 x 109/l; only one patient developed thrombocytopenia below 20 x 109/l. No patient required red blood cell transfusions and one was given a single prophylactic platelet transfusion. All patients are alive at 210-390 (median 285) days and have definite evidence of chimerism; one developed biopsy-proven GVHD on day 50, with a limited cutaneous rash. The procedure is less costly than its counterpart using myeloablative conditioning regimens and may represent another approach in the management of patients requiring an allogeneic stem cell transplant. Bone Marrow Transplantation (2000) 25, 131-133.