In order to study the behavior of the carcinoembryonic antigen (CAE), we assayed the concentrations of CEA in 67 nipple discharges of women with duct ectasia of the breast by means of a fluoroimmunoassay (EG & G. Wallac. Finland). The CEA concentrations ranged from 0.1 to 854 ng/ml (median 38.7), these being higher (p: 0.065) in the luteal phase (34 cases; range: 5.0-854, median 61.7) than in follicular phase of the menstrual cycle (29 cases; range: 0.1-452; median 30.5). Concentrations greater than 400 ng/ml were observed in two cases (2.98%) and none of the cases showed CEA values higher than 1000 ng/ml. Our results suggest that nipple discharges by ductal ectasia of the breast can be associated with increases in CEA, which can be explained by its own physiopathology, although it rarely (3%) exceeded 400 ng/ml.