Breast cancer is a major health issue and yet there lacks studies which show the correlation between Ki-67 as a prognostic marker and the variables of breast cancer. Aim: to correlate Ki-67 index with clinical and histological parameters of breast cancer. Methods and materials: it is a cross-sectional study done on 86 cases of cancer breast who presented to the institute SBMCH, Chennai in one and a half years duration. Age, tumor size, site , menopausal status, lymph node involvement ,histological type and grade, Ki-67 index were determined and correlated in these patients. Results: the mean age was 52 years, and most of them (62.8%) were post-menopausal. The tumors were more common on the left breast compared to right. Size of 2-5cm were more prevalent and more cases had nodal involvement in our study. Out of the histological types Invasive ductal was most common followed by Papillary carcinoma and Invasive lobular carcinoma. In our study Ki-67 did not show any significant correlation with the age(p=0.427), gender(p=0.447),side of the tumor(p=0.619), menopausal status(p=0.121), pathological size of the tumor(p=0.169),nodal involvement(p=0.568) or histological type of the tumor(p=0.373). However a really significant correlation was observed between grade of the tumor(p<0.001). Concluding that in our study there was a significant correlation between ki-67 and tumor grade which is an established prognostic marker, and hence it plays a vital role in deciding the prognosis of breast cancer.