OBJECTIVE: Overexpression of the p53 and HER-2/neu oncogenes are the two most common genetic abnormalities associated with breast cancer. Shorter survival time has been reported in patients with tumors with p53 or HER-2/neu. This report analyzes a retrospective cohort of early stage breast cancers for both oncogenes and relates overexpression to clinicopathologic parameters and survival. METHODS: Immunostaining for p53 and HER-2/neu was performed on 230 paraffin-embedded specimens of stage I and II breast cancers diagnosed and treated at Duke University Medical Center between 1984 and 1987. Positive staining for both p53 and HER-2/neu in paraffin-embedded tissues indicates an underlying genetic abnormality: point mutations in the p53 gene and amplification of the HER-2/neu gene. RESULTS: In this cohort of patients, 24% were positive for p53 and 17% for HER-2/neu. Four per cent were positive for both oncogenes. Significant correlations were found between p53 immunostaining and increasing tumor size, stage, and low estrogen and progesterone receptor contents. Univariate analysis showed that p53 and HER-2/neu were indicators of overall and failure-free survival. An additive effect on survival was observed in patients with both oncogene abnormalities. Nodal status, HER-2/neu, and p53 all attained independent prognostic value in a multivariate analysis. CONCLUSIONS: The p53 and HER-2/neu oncogenes have proven but limited prognostic value. An approach that combines several molecular genetic markers with established pathologic criteria may help physicians to make more accurate predictions of prognosis in patients with early stage breast cancer.