During the past 50 years, intensive studies into the use of hematopoietic stem cell transplantation (HSCT) for therapy of cancer and nonmalignant hematologic diseases have changed this treatment modality from one that was thought to be plagued by insurmountable complications to one that is now standard therapy for some diseases. More-recent research has opened up the way to include elderly patients with a wide variety of hematologic malignant diseases. Continued research by transplant teams worldwide is likely to allow continued progress toward developing novel and improved treatment modalities and even wider application of the use of pluripotent hematopoietic stem cells in the treatment of human diseases.