['To investigate the role of killer cell immunoglobulin receptor (KIR) plays in treatment of leukemia by cord blood transplantation (CBT).', 'Peripheral blood samples were collected from 23 patients receiving CBT, and corresponding cord blood samples were collected too. Polymerase chain reaction with sequence-specific primers was used to examine the genotypes of KIR and HLA-Cw of the samples. The rates of engraftment, relapse, and survival were followed up.', 'Polymorphism of KIR genotype was found in the 23 cord blood samples. In the 17 cases of acute myelocytic leukemia (AML), the engraftment rate and overall survival rate of the donors/recipients with KIR/JHLA-C mismatch was 65% and 70%, both higher than those of the KIR/HLA-C matched group (50% and 50% respectively), and the relapse rate of those with KIR/JHLA-C mismatch was 9%, lower than that of the KIR/HLA-C matched group (16%). The engraftment rate and overall survival rate of those with homo-expression of HLA-Cw1 or Cw2 were 65% and 70% respectively, both higher than those of the patients with double expression (50% and 50% respectively). There was no significant difference in overall survival rate between the HLA-Cw8 (+) and HLA-Cw8 (-) groups. Four cases with the co-expression of KIR2DL2 and KIR2DS2 all survived disease-free.'] Does [ Killer cell immunoglobulin receptor play an important role in cord blood transplantation for leukemia ]?