The role of reduced-intensity allogeneic hematopoietic stem cell transplantation (HSCT) from a variety of donor sources in improving survival for children with familial hemophagocytic lymphohistiocytosis (HLH) is well-documented. The heterogeneity of adult-onset HLH has complicated evaluation of initial therapy and of HSCT as definitive treatment. Therapy for adults with HLH is often individualized, but institutions are now generating algorithms that include HSCT based on growing experience. Consolidation of these data is needed to optimize management of the growing number of adults recognized to have HLH and to achieve dramatic improvements in survival.