The prognostic significance of preoperative serum carcinoembryonic antigen (CEA) and ferritin levels was evaluated in 191 women operated for breast cancer. The influence of CEA, ferritin and another 11 clinical and pathological features on the disease-free survival was investigated in a multivariate analysis, using Cox's proportional hazard model. Axillary node status (P = 0.004), CEA level (P = 0.011), and the histological grade of the tumor (P = 0.029) emerged as independent prognostic factors. By contrast, no significant relationship was found between ferritin and disease-free survival. These three parameters were used to derive a prognostic index (I) for each patient. Multivariate analysis showed that its prognostic value was better than the value of any single factor (P less than 0.0001). The I score was used to divide patients into groups at different risk of recurrence: low, moderate and high (97.5%, 45% and 22.5% of recurrence-free patients at 3 years respectively). The data showed that the prognosis of patients with different combinations of node status and tumor grade was related to the level of CEA. Only women with very good (node-negative with well-differentiated tumors) or very bad prognosis (node-positive with four or more metastatic nodes and poorly differentiated tumors) had a disease-free survival independent of CEA values. These findings suggest that the preoperative measurement of CEA enhances the possibility of correctly predicting outcome and hence could be of assistance in the planning of adjuvant therapies.