A study was conducted to examine whether or not the histopathological therapeutic effects of preoperative chemotherapy could be useful for determining prognosis in women with locally advanced breast cancer. The patients were 37 women with locally advanced breast cancer who received preoperative chemotherapy between 1977 and 1987. The histological grade of malignancy (HGM) and histopathological therapeutic effects of chemotherapy (TEf) were examined in resected specimens. Patients with HGM 3 showed a poorer 10-year overall survival (38%) than those with HGM 1 or 2 (62%). Patients showing a better histopathological response (TEf 1b plus 2) had a poorer 10-year overall survival (20%) than those with a poorer response (TEf 0 plus 1a) (60%). Therapeutic effects were significantly related to histological grade, nuclear atypia and mitotic index (p = 0.03, 0.005 and 0.002, respectively). Histopathological therapeutic effects were not directly correlated with patient prognosis. Cox proportional hazard regression analysis revealed that mitotic index was the most significant prognostic factor related to 10-year overall survival.