This study was designed to answer the question, do molecules with carcinoembryonic antigen (CEA) activity from colon, breast, and ovarian cancer differ? Extracts of two breast and three ovarian cancers with CEA activity were compared to three colon cancer CEA preparations and to the related antigen, colon carcinoma antigen-III, in terms of lectin- and antiserum-binding properties. With the use of Farr-type radioimmunoassays with the lectins, concanavalin A and wheat germ agglutinin, the iodinated colon CEA and CEA-like preparations from breast and ovarian cancer all showed distinctly different patterns of binding. Specificity of binding was confirmed by inhibition studies with the relevant monosaccharides. Similarly, with antisera prepared against colon CEA, colon carcinoma antigen-III, or breast CEA, it was shown that, although all preparations shared some antigens, unique antigenic determinants were also present on all preparations. These data are consistent with the concept of a series of closely related CEA and CEA-like molecules with distinct characteristics for each tissue source of CEA.