High‐dose cytoreduction and hematopoietic stem cell infusion form the basis for treatment of hematologic cancers, defects or failure of hematopoiesis, and some solid tumors. As an antitumor therapy, allogeneic hematopoietic cell transplantation (HCT) is superior to autologous HCT by induction of a graft‐us‐tumor effect. However, recipients of allografts suffer higher transplant‐related mortality owing to graft‐us‐host disease (GVHD). Nutrition support research must recognize that HCT is a heterogeneous modality whose short and long‐term outcomes are affected by transplant type, preparative regimens, diagnosis, disease stage, age, and nutritional status. The field of HCT will diversify further as lower dose cytoreduction and mixed chimerism grafts allow expansion of the technique to older patients and to other diseases. (journal of Parenteral and Enteral Nutrition 25:219–228, 2001)