In order to explore the effect of neoadjuvant chemotherapy (NACT) on clinical mid-course and pathological complete response (pCR) at surgery in different biological breast cancer subtypes. The GeparTrio study included 2,072 patients with operable or locally advanced breast cancer. After two cycles with docetaxel, doxorubicin and cyclophosphamide (TAC) patients were randomized according to their clinical response. Clinical and biological factors were assessed for predicting clinically mid-course response and pCR at surgery. The overall pCR rate, defined as no invasive residuals in breast and axilla, was 20.5%. The highest pCR rate of 57% was observed in patients below 40 years of age with triple negative or grade 3 tumors. Independent factors for mid-course response and pCR were: young age, non-T4 tumors, high grade, and hormone receptor status, the strongest single predictive factor. Within the biological subtypes, grading was an independent factor to predict pCR for luminal tumors, clinical tumor stage for the HER2 like tumors and age for the triple negative ones. Grading gave independent information for mid-course response within the triple negative group. No factor predicted mid-course response within the other groups. Grading and age can identify subgroups within the luminal and triple negative patients who have an increased benefit from NACT.