We analyzed the incidence, clinical characteristics, prognostic-factors, and outcome of central nervous system (CNS) infections in consecutive patients with receiving umbilical cord blood transplantation (UCBT) (n = 343) or HLA-matched sibling donor stem cell transplantation (MST) (n = 366). Thirty-four CNS infectioiis were documented at a median time of 116 days after transplantation (range, 7 to 1161). The cumulative incidence (CI) risk of developing a CNS infection was.6% at day +30, 2.3% at day +90, and 4.9% at 5 years. The 5-year CI of CNS infection was 8.2% after UCBT and 1.7% after MST (P<.001). The causative micro-organisms of CNS infections were fungi (35%), virus (32%), Toxoplasma spp. (12%), and bacteria (12%). Fungal infections occurred in 11 patients after UCBT and 1 after MST and were due to Aspergillus spp. (n = 8), Cryptococcus neoformans (n = 2), Scedosporium prolificans (n = 1), and Mucor (n = 1). Except for 1 patient, all died from CNS fungal infection. Viral infections occurred in 9 patients after UCBT and 1 after MST and were due to human herpes virus 6 (n = 7), cytomegalovirus (n = 2), and varicella zoster virus (n = 1). CNS toxoplasmosis was diagnosed in 3 patients after UCBT and 1 after MST. Other pathogens were Staphylococcus spp, Nocardia spp, Streptococcus pneumoniae, and Mycobacterium tuberculosis. Twenty of the 34 patients (59%) died from the CNS infection. In multivariable analysis, UCBT and disease stage beyond first complete remission were independently associated with the risk of developing CNS infections. The 5-year overall survival was 19% in patients who developed a CNS and 39% for those who did not (P =.006). In conclusion, our study showed that CNS infections are a significant clinical problem after stem cell transplantation associated with poor survival. They were more frequent after UCBT compared to MST. (C) 2017 American Society for Blood and Marrow Transplantation.