In the years since the world's first successful bone marrow transplant (BMT) was performed at the University of Minnesota in 1968, the field of bone marrow transplantation has evolved rapidly. Stem cells can be obtained from a variety of sources: bone marrow from a matched sibling or unrelated donor (allogeneic transplant), bone marrow or peripheral blood from the patient (autologous transplant), and umbilical cord blood that was collected and stored after delivery for later use by the infant, a matched sibling, or an unrelated patient. Bone marrow transplantation is a widely accepted and successful therapy for treating a variety of malignant and nonmalignant diseases. Continuing research should yield new methods to ensure successful engraftment and to prevent or reduce complications post-BMT. Many patients with cancer have been cured with BMT. However, much work remains to improve survival and to better manage complications. New approaches under investigation may expand the availability of transplantation and improve short- and long-term survival and quality of life.