In order to determine the prognostic value of c-erbB-2 protein and Epidermal Growth Factor Receptor (EGF-R), we used an immunohistochemical procedure with specific antibodies on paraffin-embedded material from a series of 73 operable breast cancer carcinomas. c-erbB-2 protein (c-erbB-2 score > 1) was overexpressed in 10/73 cases (14%) and EGF-R (EGF-R ratio > 1) in 42/73 cases (58%). c-erbB-2 overexpression was correlated with tumour size (P < 0.02) and lymph-node involvement (P = 0.05) whereas EGF-R overexpression did not correlate with any of the variables tested. The relative risk of relapse was respectively 1 vs 4.5 (P = 0.001) for patients with a negative (0-1) or positive (> 1) c-erbB-2 score and 1 vs 3 for patients with an EGF-R ratio < or = 1 and > 1 (P = 0.03). Moreover, c-erbB-2 protein overexpression is more specifically an early factor of poor prognosis whereas EGF-R overexpression is a long-term factor of poor prognosis. Patients with an early good prognosis (c-erbB-2 score = 0-1) are found to relapse with time when EGF-R is overexpressed. In a multivariate analysis including axillary lymph-node status, histological grade, tumour size, ER status, c-erbB-2 score, EGF-ratio and hormonal treatment, c-erbB-2 overexpression was the most powerful parameter (P = 0.001) followed by EGF-R overexpression (P = 0.02). We concluded that, in our series, the combined determination of c-erbB-2 protein and EGF-R appeared to be a prognostic indicator whereby both early and long term prognosis could be determined in breast cancer patients.