Objective:To study the significance of human herpesvirus type 6 (HHV-6) infection on U251 astroglioma cells and its effects on biological functions of the cells. Methods:The model of HHV-6 infection in vitro was developed by infection of U251 cells with HHV-6. Synchronized U251 were infected with HHV-6. Cytopathic effect(CPE)were visualized by inverted phase contrast microscope. u22 gene of HHV-6 was amplified by PCR. The expression of immediate early protein 1 (IE1) and late protein(gB) were determined by indirect immunofluorescence assay(IFA). The proliferation of U251 cells was determined by MTT method,and the cell cycle was detected by flow cytometry analysis(FCM). Results:After 3 days,cells infected with the HHV-6 showed the typical cytopathic effect,cell swelling and the appearance of translucence and pleomorphism. u22 gene of HHV-6 was detected by PCR. HHV-6 immediate early protein 1 (IE1) and late protein (gB) were positive in the cultured cells by indirect immunofluorescence assay (IFA). HHV-6 could promote U251 cells proliferation by MTT assay. The FCM assay showed that the cycle of the infected U251 cells changed,compared infected groups with control groups,the former G1 phase cells decreased,and cells in S phase and G2-phase increased significantly. HHV-6 could promote U251 cells proliferation. Conclusion:HHV-6 can infect the U251 cells,cause cytopathic,stimulate cell proliferation,and change cell cycle. The results of this study indicated that HHV-6 might be correlated with the genesis and development of gliocytoma,but its mechanism is not clear.