Human ovarian carcinomas express the CA-125, HER2/neu, and MUC1 tumor-associated Ags as potential targets for the induction of active specific immunotherapy. In the present studies, human ovarian cancer cells were fused to human dendritic cells (DC) as an alternative strategy to induce immunity against known and unidentified tumor Ags. Fusions of ovarian cancer cells to autologous DC resulted in the formation of heterokaryons that express the CA-125 Ag and DC-derived costimulatory and adhesion molecules. Similar findings were obtained with ovarian cancer cells fused to allogeneic DC. The fusion cells were functional in stimulating the proliferation of autologous T cells. The results also demonstrate that fusions of ovarian cancer cells to autologous or allogeneic DC induce cytolytic T cell activity and lysis of autologous tumor cells by a MHC class I-restricted mechanism. These findings demonstrate that fusions of ovarian carcinoma cells and DC activate T cell responses against autologous tumor and that the fusions are functional when generated with either autologous or allogeneic DC.