Objective To establish an animalfree culture system for human embryonic germ cells. With leukemia inhibitory factor(LIF) genetransfected human embryonic lung fibroblasts as the feeder layer. Methods Eukaryotic expression vector pcDNA3.1(+)-LIF was transfected into human embryonic lung fibroblasts. LIF positive cells were obtained after being screened by G418 and identified by RT-PCR and Western blotting. Primordial germ cells(PGCs) of 5 to 9weekpostfertilization embryos were plated onto the transfected human embryonic lung fibroblast feeder cells, and cultured in a medium without hrLIF. The cell colonies derived from PGCs were also identified. Results RT-PCR and Western blotting results showed that the transfected cells expressed LIF. Primordial germ cells that was growing on the feeder layer formed typical multicellular colonies. The colonies were found to be strongly positive in AP activities, and expressed stage specific antigens SSEA-1, SSEA-4, TRA-1-60, TRA-1-81. Oct-4 expression was positive by RT-PCR.Conclusion LIF genetransfected human embryonic lung fibroblasts as the feeder l