Most patients with myelodysplastic syndromes (MDSs) who achieve a complete remission under aggressive chemotherapy develop a recurrence within 18 to 24 months. Autologous stem cell transplantation has therefore been suggested as a potential means of increasing treatment efficacy. As compared with bone marrow stem cell autografts, peripheral stem cell autografts have a higher harvesting yield and a shorter duration of aplasia after reinjection. Also, the results reported herein suggest that polyclonal stem cells harvested after chemotherapy-induced aplasia and growth factor therapy are capable of ensuring normal hematopoiesis and may provide prolonged remissions in some patients.