Marrow transplant is potentially curative therapy for CML. Allogeneic sibling-donor marrow transplant may be the therapy of choice for younger patients early in the course of disease. Early transplant is an important influence on disease-free survival and relapse after related-donor transplant therapy, although additional patient characteristics influencing outcome can be identified and may have cumulative adverse effects. The 5-year disease-free survival of patients transplanted within one year of diagnosis and without signs of advanced disease is greater than 65%. Significant problems remain, however, including early mortality (primarily from infection, pneumonia, and pneumonitis) and relapse of CML following transplant, including late relapse occurring more than 5 years posttransplant. For patients without a matched, related donor, unrelated-donor marrow transplant may be a treatment option and can result in successful outcome for patients with CML. Relapse following unrelated-donor marrow transplant is rare. However, the use of an unrelated donor is associated with significant toxicity, including early mortality, engraftment failure, and ongoing morbidity and mortality associated with acute and chronic graft-versus-host disease. For patients who lack an available matched-related or -unrelated donor, autologous marrow transplant has been developed as an alternative approach to therapy. Long-term survival following autologous marrow transplant is possible and may even approach the survival for allogeneic related-donor recipients, although cure of disease is not achieved.