The question of whether host immune factors play a protective role in breast cancer has been long debated. Early evidence based predominantly on histopathologic changes seen in ipsolateral axillary lymph nodes was suggestive. More recently, the availability of quantitative in vivo and in vitro tests of cellular and humoral immunity in breast cancer has given further support to this concept. A number of attempts have utilized both active and passive techniques of immunotherapy, with or without cytoreductive chemotherapy, to combat the disease. This review summarizes the literature pertaining to immunology and immunotherapy of breast cancer with the hope that such knowledge may lead to further improvements in our skill in the treatment of human breast cancer.