An immunohistochemical (IHC) study of the c-erbB-2 protein was performed in paraffin-embedded tissues from 506 primary breast carcinomas. An overexpression of c-erbB-2 was detected in 32% of the tumors and was correlated with a negative estrogen receptor status, increasing tumor size as well as axillary lymph node involvement. The five-year disease free survival was analyzed in 183 patients who have been followed for at least five years. No statistically significant association of c-erbB-2 status with survival was shown. However, longer survival in women over 50 years compared to under 50 years of age was detected among the c-erbB-2 positive patients. In the multivariate Cox's regression analysis, lymph node and vascular invasions were independent prognostic indicators among these patients. But c-erbB-2 status and other factors did not predict the relapse of breast cancer. However, these data may not negate the benefit of c-erbB-2 detected by IHC for identification of patients who have a poor prognosis and require more aggressive adjuvant therapy. Further studies in a larger group of patients with longer follow-up time may provide more valid information.