We report on two patients with no active GVHD and on moderate doses of immunosuppressive drugs who unexpectedly developed fatal CMV meningoencephalitis after umbilical cord blood transplantation. A review of these two cases along with nine other cases of CMV central nervous system (CNS) disease after allogeneic SCT that were mostly reported within the last 8 years suggests that this severe complication of CMV infection may be increasing. CMV CNS disease after allogeneic SCT is a late-onset disease (median time of onset, 210 days) and is usually manifested as encephalitis in the absence of other sites of CMV disease. The development of CMV CNS disease is associated with risk factors (T-cell depletion, anti-thymocyte globulin, umbilical cord blood transplantation) that cause severe and protracted T-cell immunodeficiency (8 of 11 cases), a history of recurrent CMV viremia treated with multiple courses of preemptive ganciclovir or foscarnet therapy (11 of 11 cases), and ganciclovir-resistant CMV infection (11 of 11 cases). Despite therapy with a combination of antiviral drugs (ganciclovir, foscarnet and cidofovir), mortality is high (10 of 11 cases). Given this high mortality, extended prophylaxis with current or novel antiviral drugs and strategies to enhance CMV immunity need to be considered in high-risk patients.