Progressive experience and success in application of blood and marrow transplantation has heightened attention to clinical management of the complications and long-term outcomes of such procedures. More than 20,000 patients yearly undergo transplant therapy and more than 25,000 patients survive beyond 5 years after transplantation. The recognition, prophylaxis, management, and screening for early complications and for late effects following successful transplant have developed by extrapolation of procedures for intensive therapy of hematologic malignancy (e.g., acute leukemia) and by recognition of specific toxicities, immunodeficiencies and problems encountered uniquely by the transplant recipient.1 Similar to other hematology/oncology procedures, most management strategies are supported principally by empirically derived and some experience-supported evidence. Overall, less than one-quarter of transplant decision making is supported by Level 1 evidence. We review the approach to transplant complications through the phases of therapy emphasizing the available evidence, the frequently held consensus opinions, and areas for future study.