We reviewed our experience in 79 children who had unrelated cord blood transplant (UCBT) between 1996 and 2007 with a major focus on GVHD, comparing both traditional and National Institute of Health (NIH) criteria. The cumulative incidence (CI) of acute GVHD (aGVHD, by day +100) was 0.42 for grade II-IV and 0.22 for grade III-IV. The CI of all aGVHD (NIH, that is, no time limit) at 1 year was 0.45 for grade II-IV and 0.32 for grade III-IV. Infused CD34 cell dose (>1 × 10(5)/kg), pretransplant bacterial infection and nonmalignant disorders were risk factors for grade II-IV aGVHD on univariate analysis. Infused CD34 cell dose remained significant on multivariate analysis. At 1 year, the CI of chronic GVHD (cGVHD) using the Seattle criteria was 0.27, whereas that for cGVHD (NIH) was 0.08. By NIH criteria, the classic form of cGVHD was uncommon (5%) after UCBT. Instead, the acute (71%) and overlap (24%) GVHD variants predominated. Grade II-IV aGVHD was a significant risk factor for cGVHD by both Seattle and NIH criteria. We conclude that GVHD after day +100 after UCBT typically carries features of aGVHD. Moreover, and in marked contrast to adult unrelated donor hematopoietic stem cell transplantation, the GVHD observed in this series did not adversely affect survival.