Data from epidemiologic studies of African American women, immune studies of the effect of chemotherapy drugs and radiotherapy on immune status, and the Asian literature on the clinical benefit of polysaccharide immune therapy suggest that immune function has a role in primary and secondary prevention of breast cancer. High-priority research areas for breast cancer immunotherapy include clinical trials of Trametes versicolor (Tv) and the semipurified polysaccharide peptide Krestin (PSK). Two types of trials are called for; first, we need clinical trials of Tv as a concurrent adjuvant therapy along with chemotherapy, radiotherapy, and HER2/neu monoclonal antibody therapy (trastuzumab; Herceptin). Second, in keeping with its potential role in secondary prevention and common use of Tv in Asian oncology, we need clinical trials of Tv immunotherapy after completion of standard cancer treatment.