Although mammary epithelial cell lines can provide a rapid and reliable indicator of gene expression efficiency of transgenic animals, their short lifespan greatly limits this application. To provide stable and long lifespan cells, goat mammary epithelial cells (GMECs) were transduced with pLNCX2-hTERT by retrovirus-mediated gene transfer. Transduced GMECs were evaluated by reverse transcriptase polymerase chain reaction (RT-PCR), proliferation assays, karyotype analysis, telomerase activity assay, western blotting, soft agar assay, and injection into nude mice. Non-transduced GMECs were used as a control. The hTERT-GMECs had higher telomerase activity and extended proliferative lifespan compared to non-transfected GMECs; even after Passage 50, hTERT-GMECs had a near diploid complement of chromosomes. Furthermore, they did not gain the anchorage-independent growth property and were not associated with a malignant phenotype in vitro or in vivo.