AIM: To investigate the expression level of transcriptional factor Elf-1 in mononuclear cells, CD4~+ and CD8~+ T cells from umbilical cord blood (UCB). METHODS: Real-time PCR with SYBR green I technique was used for detecting the Elf-1 expression in mononuclear cells, sorted CD4~+ and CD8~+ T cells from 12 cases of umbilical cord blood. The relative mRNA expression level of Elf-1 was analyzed by a formula of 2~(-△Ct)×100%. The expression level of β_2-microglobulin gene (β_2M) was used as an endogenous reference. The peripheral blood from 10 cases of healthy adults was served as control. RESULTS: Elf-1 mRNA expressed in all blood samples collected from both UCB and healthy adults. The expression level showed apparent diversity in different individuals. The relative mRNA expression of Elf-1 in both mononuclear cells (18.55%±2.48%) and CD8~+ T cells (3.52%±0.45%) from UCB were significantly higher than those from healthy adults (9.16%±1.92%, 2.02%±0.27%, respectively, P<0.01, P<0.05). CONCLUSION: The results of Elf-1 expression level from umbilical cord blood indicate that the over-expression of Elf-1 gene in mononuclear cells and CD8~+ T cells might be one of the features of T cell immune state in umbilical cord blood.