Several studies have compared the results of unrelated donor bone marrow transplantation (UBMT) and unrelated donor cord blood transplantation (UCBT). To objectively analyze these data, we performed a systematic review and meta-analysis of pooled data on comparative studies of UCBT and UBMT in patients requiring hematopoietic stem cell transplantation. Combining the studies, 161 children and 316 adults undergoing UCBT (mostly 1 or 2 antigen-mismatched), along with 316 children and 996 adults undergoing UBMT (almost entirely fully matched with the recipient), were analyzed. T-cell-depleted UBMT was excluded; where data were available, only fully matched UBMT was used in the analysis. Pooled comparisons of studies of UCBT and UBMT in children found that the incidence of chronic graft-versus-host disease (GVHD) was lower with UCBT (relative risk [RR] = 0.26; 95% confidence interval [CI] = 0.12-0.57; P = .16), but the incidence of grade III-IV acute GVHD did not differ (RR = 1.46; 95% CI = 0.42-5.03; P = .55). There was no difference in 2-year OS in children when studies were pooled (RR = 0.76; 95% CI = 0.31-1.87; P = .55). For adults, transplantation-related mortality (pooled estimate, 1.04; 95% CI = 0.52-2.08; P = .91) and disease-free survival (DFS) (pooled estimate, 0.59; 95% CI = 0.18-1.96; P = .39) were not statistically different. Because of the unavailability of randomized controlled trials, pooled analysis of nonrandomized comparative studies was performed. Thus, our meta-analysis confirmed that UCBT in children and adults had consistently equivalent survival outcomes compared with UBMT despite greater donor-recipient HLA disparity with UCBT.