Objective: To investigate the effect of c-myc and fas gene cotransfection on proliferation of transplanted tumor of tongue squamous cell carcinoma cell line Tca8113 and its mechanisms. Method: The model of transplanted tumor of Tca8113 cell was first formed. Lipofectamine (control group), mixture of lipofectamine and plasmid pBK-fas (fas group), mixture of lipofectamine and plasmid pBK-fas and pcDNA3-c-myc (cotransfection group) were transfected into transplanted tumor, respectively. Growth of neoplasm was observed and recorded regularly. Animals were sacrificed and tumor specimens harvested 24 days following transfection. Fas gene expression in each neoplasm was assessed by reverse transcription-polymerase chain reaction (RT-PCR). Apoptosis and proliferation and expression of fas protein in tumor tissue were measured by flow cytometry. Results: Growth inhibition was found in both fas and cotransfection groups. Difference in growth inhibition rate between the two groups showed no significance. RT-PCR and flow cytometry suggested that fas-transfection and c-myc/fas cotransfection up-regulated expression of fas mRNA and protein, increased apoptosis index, especially in cotransfection group. No effect on proliferation index was released by fas transfection alone by cotransfection raised it. Conclusions: Growth suppression in transplanted tumor caused by fas-transfection and c-myc/fas cotransfection might be associated with up-regulation of expression of fas gene and enhancement of apoptosis.