Abstract: Objective :To investigate the potential role of tumor necrosis factor-a (TNF-α) in inducing apoptosis of murine B16 melanoma cell and in inhibiting the growth of B16 cell Xenograft in C57BL/6 mice. Methods :Cultured murine B16 melanoma cells were treated with TNF-α in different concentration for 36 hours.Flow cytometry and In situ terminal deoxynucleotidual transferase and nick translation assay (TUNEL) were applied to detect the apoptotic rate of different groups of B16 cells.The inhibitive effect of TNF-a!on B16 cell xenograft growth was studied in vivo by admistering TNF-α with a small dose every day locally. Results :TNF-a. could significantly induce apoptosis of B16 cells at the concentration of 1 000 3 000 5 000 and 10 000U/mL (P<0.01), and the apoptotic rate of B16 cells was TNF-α concentration dependent. After treated with TNF-a for three weeks, the volume and the weight of tumor in C57BL/6 mice were significantly less than that of controls (P<0.01). Conclusion :TNF-α can induce the apoptosis of murine B16 melanoma cells,and TNF-a injection with a small dose could inhibit significantly the growth of transplanted MM.