To establish a cell line for stable expression of human beta-defensin 3 (hBD3). Methods Full length cDNA of hBD3 was isolated from previously constructed pGEM-hBD3 and then inserted into pcDNA3. The recombinant vector identified carrying hBD3 with right direction was introduced into COS-7 cells by Lipofe-ctamine. Cell clones survived in G418-rich medium and with stable expression of hBD3 in both mRNA and protein levels were identified by RT-PCR and Western blot respectively. Genomic integration of the hBD3 gene with the COS-7 cells was confirmed by Southern dot blot and primary analysis. The antimicrobial activity of the secreted hBD3 was also evaluated. Results COS-7 cells transfected with pcDNA3-hBD3 expressed hBD3 stably in mRNA and protein level. Southern dot blot analysis showed successful integration of the hBD3 gene into the genome of COS-7 cell and the hBD-3 protein secreted into the culture medium showed antimicrobial activity. Conclusion We successfully established a hBD3-expressing cell line. To establish a cell line for stable expression of human beta-defensin 3 (hBD3). Methods Full length cDNA of hBD3 was isolated from previously constructed pGEM-hBD3 and then inserted into pcDNA3. The recombinant vector identified carrying hBD3 with right direction was introduced into COS-7 cells by Lipofe-ctamine. Cell clones survived in G418-rich medium and with stable expression of hBD3 in both mRNA and protein levels were identified by RT-PCR and Western blot respectively. Genomic integration of the hBD3 gene with the COS- 7 cells was confirmed by Southern dot blot and primary analysis. The antimicrobial activity of the secreted hBD3 was also evaluated. The results of Southern blot analysis showed successful integration of hBD3 expressed hBD3 mRNA and protein level the hBD3 gene into the genome of COS-7 cell and the hBD-3 protein secreted into the culture medium showed antimicrobial activity. Conclusion We successfull y established a hBD3-expressing cell line.