Using the murine BW5147 tumor model system, we have identified 3 MAbs that discriminate between metastatic and non-metastatic BW5147-derived T-cell hybridomas and BW5147-unrelated T-lymphomas. The 3 rat MAbs appear to recognize an identical membrane-associated sialoglycoprotein with an approximate molecular weight of 95-100 kDa. We thus defined "metastatic T-cell hybridoma" antigens (MTH-Ags) that are also expressed on normal T-lymphocytes. No correlation was found between the expression of the MTH Ags and in vitro invasive behavior of normal and malignant cells. Neither did we find any relationship between organ specificity of i.v. inoculated tumor cells and their MTH-Ags expression. It thus remains unclear whether our MTH-Ags are functionally involved in the metastatic process, or whether their expression is only incidentally related to the metastatic potential.