Activation of the cell-surface antigen CD95 induces apoptosis of CD95-bearing tumor cells. In this study, we investigated the antitumor effect of locally produced CD95 ligand (CD95L) on CD95-negative tumor cells in vivo. Introduction of CD95L cDNA into murine tumor cells did not affect growth in vitro but caused rejection in vivo. Neutrophils were primarily responsible for this rejection. A CD8 T cell-mediated protective immunity against subsequent challenge with parental tumor cells was also elicited. These results provide evidence for the potential utility of CD95L in tumor eradication and also reveal a proinflammatory function of CD95L.