Hematopoietic stem cell transplantation has become increasingly important in the treatment of hematologic malignancies over the past 20 years. While it is associated with significant morbidity, it offers the only chance of cure in many circumstances. Autologous and allogeneic transplantation have been used successfully to treat a variety of hematologic malignancies. These 2 approaches offer different risks and benefits which are discussed in this review. Timing of transplantation and selection of patients are also discussed. New innovations in stem cell transplantation including umbilical cord blood and non-myeloablative transplantation are reviewed.