Histological assessment of the therapeutic response to neoadjuvant therapy gives us information regarding the efficacy of a given treatment in individual patients. Such information is useful for guiding selection of appropriate therapeutic strategies after surgery. In many studies of neoadjuvant chemotherapy (NAC) for breast cancer, both the histological therapeutic effect in the primary lesion and the lymph node metastatic status are significantly related to prognosis. The histological assessment of therapeutic response helps determine prognosis in breast cancer treated with NAC; however, methodological problems remain. There are many different histological criteria currently used to assess therapeutic response. Even when the same criteria are used, use of different methods for examination of surgical material can cause different results for the same patient case. When histological therapeutic effect is determined in daily clinical practice, pathologists have to describe the criteria used and their examination methods. Histological criteria for evaluation of therapeutic response and methods for examination of surgical materials after neoadjuvant therapy must be standardized in the near future.