Charts and radiographs of 622 allogeneic hematopoietic stem cell transplant (HSCT) recipients, over a 20-year period, were retrospectively reviewed for intracranial hemorrhage (ICH) following transplant. A total of 21 cases of ICH were identified (3.4%) including 15 cases of intraparenchymal hemorrhage (IPH), two cases of subarachnoid hemorrhage (SAH), and four cases of subdural hematoma (SDH). The median time from transplantation to the onset of ICH was 63 days (range, 6-3,488 days). The clinical features of post-transplant ICH patients were similar and included hypertension, diabetes mellitus, chronic graft-versus-host disease (GVHD), systemic infection, and veno occlusive disease (VOD), recently referred to as sinusoidal obstruction syndrome, in addition to severe thrombocytopenia. Mortality rate was especially high (89%) after IPH with a median survival of 2 days (range, 0-148 days). In contrast, all patients with SAH or SDH following HSCT survived. The cause of post-transplant ICH appears to be multifactorial, including thrombocytopenia, hypertension, acute GVHD, VOD, and radiation therapy. Most patients in our series displayed severe thrombocytopenia at the onset of ICH, even though adequate prophylactic platelet transfusions were given. By univariate analysis, cord blood transplantation, acute GVHD, systemic infection, and VOD were related to the incidence of ICH, whereas prior CNS episodes and radiation therapy did not reach statistical significance. A multivariate analysis with logistic regression identified acute GVHD as the only factor that significantly influenced ICH occurrence.