To study the therapeutic effects of herpes simplex virus thymidine kinase gene transferred by the EBV based expression vector on experimental hepatocellular carcinoma, pDR2 TK gene was delivered into human hepatocellular carcinoma cell line SMMC 7721 by using liposome mediated transfection technique,and then gene expression was detected by RT PCR, and the killing effects were examined through MTT method. In the nude mice hepatoma model,the antitumor effects of pDR2 TK /GCV system was evaluated in terms of tumor growth. MTT results showed that the pDR2 TK /GCV had cytotoxic effect and about 70 % SMMC 7721 cells were killed when GCV was at 1000 μmol/L. In vivo experiment showed that the tumor size in nude mice with transferred pDR2 TK gene was significantly smaller than that in control group . On the 10th day the tumor in 3 mice (60 %) disappeared completely after GCV treatment. It is concluded that the pDR2 TK/GCV system has marked killing effects on the experimental hepatocellular carcinoma. To study the therapeutic effects of herpes simplex virus thymidine kinase gene transferred by the EBV based expression vector on experimental hepatocellular carcinoma, pDR2 TK gene was delivered into human hepatocellular carcinoma cell line SMMC 7721 by using liposome mediated transfection technique, and then gene expression was detected by RT PCR, and the killing effects were examined through MTT method. In the nude mice hepatoma model, the antitumor effects of pDR2 TK / GCV system was evaluated in terms of tumor growth. MTT results showed that the pDR2 TK / GCV had cytotoxic effect and about 70% of SMMC 7721 cells were killed when GCV was at 1000 μmol / L. In vivo experiment showed that the tumor size in nude mice with transferred pDR2 TK gene was significantly smaller than that in control group. On the 10th day the tumor in 3 mice (60%) disappeared completely after GCV treatment. It is concluded that the pDR2 TK / GCV system has marked killing effects on the experimenta l hepatocellular carcinoma.