50 patients with advanced metastatic breast cancer were matched into 25 "twin" pairs. In each pair, one "twin" received chemotherapy (FAC) and the other received chemoimmunotherapy (FAC + intratumorally Propionibacterium granulosum KP-45 (PG)). The therapeutic effects of this 2-year follow-up study were carefully documented and analysed. The mean survival time of FAC + PG-treated patients was about 17 months as compared to 8.5 months in FAC controls. PG-therapy responders showed increasing values of T-lymphocytes in peripheral blood, as well as higher blast transformation indices than nonresponders and controls. The skin reactivity to PHA, Distreptase, and Tuberculin was markedly enhanced in the FAC + PG-group. The incidence rate of hematological and/or infectious complications was significantly lower in PG-treated patients than in the controls. Local PG-immunotherapy was proven beneficial in advanced breast cancer when combined with FAC-chemotherapy, providing better toleration of chemotherapy and lower risk of myelosuppression and infections.