PURPOSE: Reliable prognostic factors, including clinicopathological parameters (Ed-alternatively, "Reliable clinicopathologic prognostic factors") such as tumor size, axillary lymph node involvement, histologic grade, menopausal patient status and steroid receptor status, are necessary in the management of breast cancer for predicting clinical course and as guide lines for adjuvant therapy. Recently, many reports have shown that expression of p53 and c-erbB-2 products is associated with poor prognosis. To elucidate the clinical value of p53 and c-erbB-2 protein expression as prognostic factors, their immunoreactivities were compared with known clinicopathologic prognostic factors. METHODS: The expressions of p53 and c-erbB-2 proteins were analyzed by immunohistochemical method with formalin-fixed and paraffin-embedded tissue samples of 71 invasive breast carcinomas accumulated between 1996 and 1999 at Chungbuk National University Hospital. The expressions of p53 and c-erbB-2 proteins were compared with established prognostic factors such as tumor size, axillary lymph node involvement, histologic grade, menopausal patient status and steroid hormone receptor status. Statistical significance was analyzed by chi-square test. RESULTS: The immunoreactivities of p53 and c-erbB-2 proteins were detected in 29.6% and 46.5%, respectively, of the samples. p53 positivity was significantly higher in breast carcinoma that showed higher histologic grade or was metastasized to more than 3 axillary lymph nodes (P<0.05). There were no significant correlations between c-erbB-2 positivity and known clinicopathologic prognostic factors. CONCLUSION: This study suggests that expression of p53 protein could be used as a prognostic indicator in the management of breast cancer. But the impact of p53 and c- erbB-2 protein expression on overall survival and disease free survival rates should be evaluated further before being used as independent prognostic factors.