The antigenic phenotypic repertoire of MCF-7 human breast carcinoma cell line variants that display different sensitivity to adriamycin (Adr) was analyzed using monoclonal antibodies (MoAbs) recognizing five different tumor associated antigens (TAAs) and the external domain of the epidermal growth factor receptor (EGF-R). ELISA and cytofluorimetry determinations were used and results indicate a diminished expression of one antigenic determinant of the carcinoembryonic antigen (CEA) molecule, the disappearance of all the other TAAs and the de novo expression of the EGF-R in the MCF-7 AdrR (IC50/Adr:10 uM). Treatment with recombinant alfa-Interferon (alfa-IFN) did not enhance antigenic expression in MCF-7 AdrR cells.