Abstract: Objective:To discuss the relationship between the DNA content, ploid distribution and the clinical significance and gene therapy for pleomorphic adenoma of salivary gland. Methods: Fifty cases of pleomorphic adenoma and 10 cases of salivary gland were determined by flow cytometry, the HSV一tk gene was transfected into human benign and adjacently malignant pleomorphic adenoma cells of salivary gland respectively using recombinant adenovirus vector. The efficiency of transfection and expression were detected by RT-PCR. The inhibition of cell proliferation was verified by MTT. Results: The aneuploid y rate of pleomorphic adenoma was obviously higher in young patients with large tumor or with the cause of disease shorter than 2 years (P<0.05). The proliferation of pleomorphic ade-noma cells infected by HSV一tk gene was inhibited and the survival rates of the diploid cells at day 3 and day 5 were 78.3% and 37.7%, respectively, but the aneuploidy cell survival rate decreased to 27.6% and 27.2% at day 3 and days 5, so the survival rate of the diploid cells was significantly higher(P<0.05). Conclusions: 1) To evaluate the DNA ploidy of pleomorphic adenoma is valuable for diagnosis and treatment. 2) The lethal effect of HSV一tk gene on the aneuploidy cells is obviously much more powerful compared to diploid cells.