Complexes containing glycoproteins and glycosaminoglycans were released into the culture medium by both smooth and skeletal muscle cells. The particles, termed adherons, from three smooth muscle cell lines promoted cell-substratum adhesion of a clonal sympathetic nerve cell line, PC12. In contrast, the glycoprotein complexes from three skeletal muscle preparations inhibited the adhesion of PC12 cells to Petri dish surfaces. The skeletal muscle adherons all sedimented in calcium-free sucrose gradients with an S value of 16, while the smooth muscle particles had a sedimentation value of 12. Although both classes of adherons contained fibronectin and collagen, hyaluronic acid was present only in those from skeletal muscle. An antiserum prepared against skeletal muscle adherons blocked myoblast adhesion to skeletal muscle adherons but did not alter PC12 adhesion to smooth muscle adherons. These data suggest that the glycoprotein complexes released by muscle have some intrinsic specificity with respect to their ability to mediate cellular adhesion.