It is clear, then, that cryosurgery augments immunity that is specifically directed against the tumor in several murine tumor systems. Both cell-mediated and humoral immunity are involved. The degree of augmentation of immunity is greater than that following a period of tumor growth and cold-knife excision and that following electrocoagulation of tumor. The degree of tumor-specific immunity after cryosurgery is not sufficient to alter growth rates of recurrent tumors, however. Although immunity is not markedly potentiated, it is sufficiently augmented to be effective in protecting against small doses of tumor cells of up to 10(6) cells, and presumably in the presence of minimal residual disease. It is possible that immunity could be potentiated further by the injection of accessible tumors with a nonspecific immunoadjuvant one to five days before cryosurgery.