Neoadjuvant chemotherapy is an essential therapeutic approach for breast cancer patients, with the goal of improving pathological complete response rate (pCR) by decreasing staging and evaluating treatment response for prognostic purposes. Proliferation index estimated by Ki 67 has a significant impact on the tumour prognosis with cut off value 30%. However, data is still insufficient about the predictive cut-off value for pCR after neoadjuvant chemotherapy. The objective of this study is to evaluate the pathologic response after neoadjuvant chemotherapy in breast cancer patients, to examine the impact of Ki67 index on the rate of pathologic response with estimation of the proper predictive cut off value. We also studied the correlation of pCR rate with different prognostic histopathological parameters. Methods: The study included 84 cases of breast cancer patients received neoadjuvant chemotherapy. Baseline Ki67 immunohistochemical expression was evaluated. Results: 25% of the patients achieved pCR. The optimal cutoff point for Ki67 is 25%. There is a significant correlation between pCR and tumour infiltrating lymphocytes (TILS), T stage before therapy, lymph node metastasis and postmenopausal state. Linear regression analysis showed that Ki67 and TILs were associated with an increased rate of pCR after neoadjuvant therapy with a high significant correlation. Conclusion: In breast cancer patients, Ki67 expression with a cutoff threshold of 25% could be used to predict the probability of achieving a complete response to neoadjuvant therapy. TILs are strongly associated with pCR. Keywords: Breast cancer, pCR, Ki67, neoadjuvant therapy, IHC, TILs.