INTRODUCTION Early observations suggesting some cancer patients can mount a therapeutic immune response to their own tumors (reviewed in Ref. 1) have supported long-standing efforts to develop immunotherapy regimens for the adjunct treatment of human neoplastic disease. Immunotherapy protocols are classified as either passive or active specific, depending on how they are designed to deliver the desired immunity to the patient. Passive immunotherapy regimens are characterized by the passive administration of immune effector components such as lymphokines, antibodies, cytotoxic T cells, or lymphocyte-activated-killer (LAK) cells. By contrast, active specific immunotherapy (ASI) regimens actively induce effector mechanisms and tumor immunity in the patient by deliberate vaccination with a tumor cell or its antigenic components. The ASI approach is preferred because the resulting immunity is longer lasting, and a potential memory response may provide beneficial immune surveillance in the host against further outgrowth of the tumor.