Carcinoembryonic antigen is widely used as a tumor marker for gastrointestinal neoplasms. Its role in the management of other tumors is poorly defined. This review considers the place of carcinoembryonic antigen measurement in the management of breast cancer and concludes that sufficient data exist to support its use in clinical practice. Of the many potential uses, the major role for carcinoembryonic antigen measurement in breast cancer is in following patients with advanced disease, especially patients with bone metastases.