Abstract: Objective: The cytotoxicity of murine peritoneal elicit macrophage（PEMф） infected by NDV-L was studied in vitro. Methods: This study was carried out by electronic microscope, ³H-TdR and Griess assay. Results: （1）Under the optical microscope and scan electronic microscope, the shape of the PEMф changed markedly comparing with the control group, while the NDV-L infected PEMф for 24 hours; （2）When the activated PEMф infected by NDV-L acted on H₂₂ and P₈₁₅ tumor cells, a significant tumorcidal effect was found and the cytotoxicity was nearly the same as that in the positive group （BCG-LPS-PEMф）; （3）while infecting murine PEMф for 24 hours, NDV-L could induce the PEMф releasing nitric oxide （NO）. Conclusion: The PEMф activated by NDV-L may kill H₂₂ and P₈₁₅ tumor cells and this function seems to be related with NO releasing.