Background Umbilical cord blood (UCB) has grown substantially as an altative source of hematopoietic stem cells for unrelated donor transplantation in both adult and pediatric patients.Our aim was to assess the leukemia-free survival (LFS) and some primary results,such as hematologic recovery,risk of graft-versus-host disease (GVHD),relapse,and long-term survival,after unrelated cord blood transplantation compared with the outcomes of transplantations from other unrelated graft source.Methods The clinical outcomes of 112 consecutive patients with acute leukemia who received umbilical cord blood (UCBT) as a primary unrelated stem cell source (n=38),bone marrow (UBMT n=28,transplanted before January 2003),or peripheral blood stem cells (UPBSCT n=46,transplanted after January 2003) between July 2000 and July 2008 were analyzed.Results Except that the patients were much younger in the UCBT group (median age,10.5 years in UCBT,30 years in UPBSCT,and 20 years in UBMT),other pre-transplant parameters,such as gender,diagnosis,and the phase of disease,were comparable.All patients received myeloablative regimens,primarily including BUCY; however,there was less antithymocyte globulin (ATG) used for the UBMT patients (2138 in UCBT,0/46 in UPBSCT,and 8/28 in UBMT did not use ATG,P=0.000).Significant delays in engraftment occurred after UCBT for both neutrophil cells and platelets.The cumulative allo-engraftment rates were also significantly lower (87.8％ vs.97.8％ vs.100％ for WBC,P=0.000; 73.0％ vs.97.5％ vs.89.5％ for PLT,P=0.000) for UCBT.The incidence of Grade 2-4 and 3-4 acute graft versus host disease (aGVHD) was much higher in the UBMT group but did not differ among the other groups (51％ and 13.2％,40.2％ and 10.5％,and 77.4％ and 41.2％,respectively,for UCBT,UPBSCT,and UBMT,P=0.000).The occurrence of extensive chronic GVHD (cGVHD)was significantly decreased for recipients of UCBT (4％) compared with that of UPBSCT (39.1％) and UBMT (49.1％,P=0.000),although the rates of whole cGVHD were not significantly different (30.3％,63.1％,and 60.1％ for UCBT,UPBSCT,and UBMT,respectively).The patients had a similar rate of CMV infection (21/38,28/46,and 22/28 for UCBT,UPBSCT,and UBMT,respectively),while the HC occurrence was lower after UCBT (7/38,16/46,and 14/28 for UCBT,UPBSCT,and UBMT,respectively).As of August 2012,there was no apparent difference in 5-year overall survival (OS),LFS,or the relapse rate for each graft source (52.5％,52.6％,and 20.8％ in UCBT; 48.7％,46.4％,and 27.9％ in UPBSCT;and 46.4％,42.9％,and 16.0％ in UBMT).Conclusion These data support the use of UCB donors as an altative allogeneic donor.