The knowledge of immunological reaction against tumor results in using of immunological methods in identification and characterisation of tumor antigens, and also in diagnosis and prognosis of malignant diseases. Identification of tumor antigens by monoclonal antibodies has been an important development in breast cancer research. A number of monoclonal antibodies produced against breast cancer antigens do not detect "tumor-specific" antigens, but, rather, they react with normal or modified tissue antigens which are inappropriately expressed upon malignant cells. The application of several monoclonal antibodies in combination has a potential value in immunohistopathology as diagnostic tools for recognition of small quantities of malignant cells, of premalignant changes, of histological origin of the metastases, or in the development of serum assays for tumor markers. Some of monoclonal antibodies produced against breast cancer antigens, and also attempts of their application in the diagnosis and prognosis of breast cancer, are presented in this review.