Prospects for a new biologically based strategy of cancer treatment are being discussed. While physically and chemically based therapies, such as radio- and chemotherapy, are not directed against cancer tissue only and have a suppressive effect on the immune system, immunotherapy and gene therapy, which are discussed here, try to be more selective and to stimulate rather than suppress antitumor immune mechanisms. On the basis of personal experience with these new technologies, good future prospects are predicted for the application of cancer vaccines and immune T lymphocytes for active specific immunization (ASI) and adoptive immunotherapy (ADI) respectively. While ASI strategies aim at micrometastases being affected by activated host immune T cells, and might find a place for postoperative adjuvant treatment in high-risk cancer patients, cellular therapies such as ADI do not require an intact host immune system and could therefore also find application in advanced stages of disease. In spite of the exciting new perspectives of immuno- and gene therapy for the cancer patient, this therapy is not yet a defined discipline and requires years of further research.