The ongoing development of monoclonal antibody technology may eventually lead to the selective targeting of human carcinoma lesions by MAbs conjugated with a variety of cytotoxic agents (i.e., radionuclides, drugs, etc.). The antigen phenotype of the carcinoma cell will play an important role in the efficacy of the MAbs. Clearly, the human tumor antigens that are expressed on all carcinoma cells, and with a high antigen density, should provide the optimal target for the MAbs. More often than not, however, the human tumor antigens whose expression is highly selective for human tumor cells will also exhibit a certain degree of heterogeneity. Therefore, the ability of interferon to augment the level of expression of human tumor antigens such as TAG-72 and CEA, may play an important role in an adjuvant setting for immunoscintigraphy and/or immunotherapy. More recent observations have demonstrated that interferon treatment can also enhance the amount of TAG-72 and CEA secreted by the tumor cell. The ability of interferon to enhance the shedding of both TAG-72 and CEA could be of particular importance since recent reports suggest that their presence in the sera of patients diagnosed with gastrointestinal adenocarcinoma may be complementary and that the ability to increase either marker may facilitate earlier diagnosis of recurrent disease. It is conceivable that in subsequent years effective approaches to monitoring and/or treating malignancies may include a new combination of biological/immunological therapy.