Bone marrow transplantation for treatment of certain hematologic and nonhematologic diseases is rapidly becoming the treatment of choice for a large number of patients. Over 10,000 marrow transplants have been performed, and over 200 marrow transplant units currently exist. Complex medical and nursing care from marrow transplant teams is required to care for the acute and chronic complications associated with this treatment. This article addresses the history and process of marrow transplantation and nursing assessments and the interventions needed to care for marrow recipients, their donors, and their families.