Cancer immunotherapy is not a standard in clinical treatment of tumors, while first attempts were made several years ago. The appearance of tumor specific antigens (TSA) e.g. Bcr/abl, or tumor associated antigens (TAA) in cancer cells may be used theoreticaly in cancer therapy. Tumor cells in transformation process accumulate products of oncogenes and/or loss the functional products of tumor suppressor genes. This processes change intracellular signaling roads regulating cell proliferation and/or apoptosis of cancer cells and effect the tumor growth progression. Tumor progression is, however, not only due to genetic transformation of cancer cells but as well to changes in response to the tumor of immunological system of the organism. The immunological tolerance of the organism develop in cancer, the situation when cancer cells and cytotoxic T cells (CTLs) coexist. The attack of CTL against tumor cells is blocked. Predendritic cells (pDC) are present in tissues, and they endocytose virally infected or pre-cancer cells. Then the pDC translocate to peripheral lymphatic tissue e.g. lymph nodes where they mature to dendritic cells (DC) and cross-present the antigens of infected cells or cancer cells to naive T cells CD8+ and CD4+. The antigens of apoptotic cells may be cross-presented by DC to T lymphocytes as well, and probably chaperone proteins (hsp) are involved in this process. The above observations were used to stop the immunological tolerance in cancer as part of immunotherapy. The scheduled procedure is, first surgical removal of the tumor. The tumor tissue is divided on portions and banked in liquid nitrogen. Then, about one months after surgery, the tumor tissue is recovered from the bank, tumor cells are isolated and ex vivo irradiated or treated with Mafosfamide (Maf) with a dose sufficient to block cell divisions, but not to kill the cells. The cell suspension is than injected s.c. to the patient four times in one week intervals. The activation of immunological system should induce removal of cancer cells remaining after surgery. The clinical results in colon cancer immunotherapy are similar as in chemotherapy after surgery. It is important, that immunotherapy does not expose the patient to bacterial, viral or fungal infections and does not induces secondary cancers as compared to chemotherapy.