Tumor immunogenicity has been increased in a mouse model system by chemical modification of the tumor cells. Using peripheral blood lymphocytes as responder cells, freshly explanted human ovarian cell carcinoma cells function well as both an alloimmunogen and target cells in cell-mediated cytotoxicity assays. BIBLIOGRAPHIC REFERENCES: Yust, I., Smith, R., Wunderlich, J., and Mann, D.: Temporary inhibition of antibody-dependent, cell-mediated cytotoxicity by pretreatment of human attacking cells with ammonium chloride. J. Immunol. 116: 1170-1172, 1976. Steinmuller, D., Rodman, S.A., and Wunderlich, J.: Epidermal cells as targets and stimulators of allograft immunity in vitro. Transplant. Proc. 9: 1183-1185, 1977.