211 patients with various stages of breast cancer were studied by both the CA 15.3 and CEA markers to assess whether the latter may increase the screening sensitivity of the former. While both markers were equally specific, CA 15.3 was seen to be much more sensitive than CEA (p less than 0.0001). Also, the addition of the CEA did not add appreciably (7%) to positive detection by CA 15.3. There appears to be no advantage to including CEA in a marker panel to follow the course of breast carcinoma.