Seven male patients in the David T Purtilo International X-linked Lymphoproliferative Disease (XLP) Registry have undergone allogeneic hematopoietic stem cell transplantation (HSCT). All patients received HSCT from HLA-identical donors: sibling BM, five; unrelated BM, one; and sibling umbilical cord blood, one. Ages at time of HSCT ranged from 5 to 30 years. Pre-HSCT clinical course varied, but four boys had a significant history of chronic and/or serious infections. Conditioning regimens varied: TBI containing regimens, four, chemotherapy only, three. All patients engrafted. Six developed grade I-II acute GVHD but no chronic GVHD. Four are alive and well with normal immune function greater than 3 years following HSCT. Three died within 100 days: disseminated adenovirus, one; polymicrobial sepsis, one; and multiple organ system failure and bleeding diathesis, one. No EBV-associated post-transplant complications were observed, even though all donors except the umbilical cord blood were EBV-seropositive. Unsuccessful HSCT was associated with age at HSCT (> 15 years), TBI-containing regimen and significant history for pre-HSCT infections. These results provide evidence that HSCT performed during childhood with HLA-identical sibling donors, regardless of EBV serostatus, offers the only curative therapy for XLP.