A highly metastatic murine tumor line (ESb) and a plastic-adherent variant derived from it (ESb-M) were compared for expression of cell surface glycoproteins. Previous studies had shown that ESb-M cells were very similar to ESb cells in terms of cell surface marker expression and invasive capacity in vitro, but studies in vivo revealed that they exerted a decreased metastatic capacity. Syngeneic animals inoculated SC with ESb-M cells developed larger primary tumors and survived much longer than animals inoculated similarly with ESb cells. When using the lectin soybean agglutinin (SBA), distinct differences were observed in the glycosylation of a 220 kDa and a 80 kDa cell surface glycoprotein. Further differences in expression of cell membrane proteins were detected by means of variant-specific monoclonal antibodies. These specific ligands reacted with 65-75 kDa membrane glycoproteins, which were more prominent in ESb-M cells than in ESb cells. Apart from these differences, the two cell lines showed very similar profiles of membrane glycoproteins and lectin staining. Whether the structural differences seen in cell surface proteins can explain the changes in functional behavior (metastatic behavior and plastic-adhesive properties) of the cells remains to be investigated.