Plasma membrane glycoproteins are involved in cell-matrix interactions. For identification of such glycoproteins a recently developed cell system was used. Two cell populations differing in their adhesion properties were selected from Morris hepatoma 7777. One population was able to grow as a monolayer, while the other proliferated in suspension. From both cell lines spontaneous revertants were selected. By using antibodies raised against plasma membranes of the hepatoma and of rat liver for sequential immunoprecipitation a glycoprotein of Mr 110000 was identified. This glycoprotein was only expressed in adherent hepatoma cells as well as in normal rat liver, but was absent in non-adherent hepatoma cells and in the in vivo growing Morris hepatoma 7777. This suggests that the glycoprotein is involved in cell-substratum adhesion of hepatocytes and adherent hepatoma cells.