Abstract: Eliciting a systemic antitumor immune response, in a patient who presents with or who is at risk of developing multiple metastatic tumors of a given cell type, entails, in one embodiment, inoculating a tumor in the patient with a pharmaceutical composition consisting essentially of (A) a herpes simplex virus (HSV) that infects tumor cells but that does not spread in normal cells and (B) a pharmaceutically acceptable vehicle for the virus, such that an immune response is induced that is specific for the tumor cell type and that kills cells of the inoculated tumor and of a non-inoculated tumor. In another embodiment, the pharmaceutical composition also comprises a defective HSV vector which contains an expressible nucleotide sequence encoding at least one immune modulator. In another embodiment, the pharmaceutical composition contains a second HSV that infects tumor cells but that does not spread in normal cells.