These studies involve the generation and utilization of monoclonal antibodies (MAbs) to identify and characterize human carcinoma associated antigens and differentiation antigens of mammary and colonic epithelium. These MAbs are being used to better understand the cell biology and pathogenesis of human carcinomas, and to provide reagents for use in several aspects of the management of several human carcinomas. These include: detection of occult tumor cells, further defining the degree of differentiation of carcinoma cell populations, serum antigen assays, and radiolocalization of primary and metastatic carcinoma lesions in situ (and potentially therapy) using radiolabeled monoclonal immunoglobulins. These studies are divided into four areas of investigation: (I) The generation and characterization of an MAb that defines a novel tumor associated antigen (TAG-72) (II) The development and characterization of MAbs to a repertoire of epitopes on carcinoembryonic antigen (CEA) which are differentially expressed among carcinoma cell populations, (III) The definition and characterization of breast and colon associated antigens and (IV) The generation and characterization of B72.3 second generation antibodies to further define the TAG-72 antigen and for potential utility in carcinoma management.