There is considerable need for reliable prognostic markers to guide clinicians in management decisions for the breast cancer. The cell cycle is governed by a family of cyclin-dependent kinases (Cdks). regulated by associated cyctin. p27, a cyclin dependent kinase inhibitors, regulates progression from GI into S phase by inhibiting cyclin/cdks complex. This study was performed to evaluate the association between p27 expression, determined by immunohistochemical stain, and various histopathologic features in breast cancer. It was also determined whether p27 expression had the significance as the prognostic factorin the breast cancer patients. 45 patients who got the relatively good preserved paraffin blocks among the 100 patients was chosen for immunohistochemical staining against p27, cyclin E, c-erbB2, cathepsin D and p53 and reexamined their nuclear and histological grades from Jan. 1989 through Dec. 1992. As a results, the patients with negative expression of p27 had more metastatic axillary nodes than those with positive expression. (5.87±1.87 vs 1.14±0.54, p=0.021) p27 negative group got worse nuclear grade than p27 negative group but beyond statistical significance. (48.4% vs 28.6%, p=0.281) On univariate analysis, primary tumor size, status of axillary nodes and the expression of p27 were the significant prognostic factors affecting overall survival rates. In particular, p27 positive group had better outcomes on 5 years survival rate than p27 negative group. (92.31±7.39% vs 73.33±8.07%, p=0.0441) but didn't affect the disease free survival with statistical significance. On multivariate analysis, the primary tumor size and axillary node were significant prognostic factors on overall and disease free survival. In conclusion, despite relatively small size of this study group, considering that p27 negative group got the more metastatic node and worse overall survival, p27 expression might be a novel prognostic indicator in the breast cancer.