Fibronectins comprise a class of high molecular weight glycoproteins present both in extracellular matrices and in soluble form in body fluids. Although they have been studied for about forty years, their real significance emerged only during the past decade. Intensive research has focused on their role in platelet function, cell migration, the cytoskeleton, reticuloendothelial function, and on alterations in fibronectin distribution during development and disease. Fibronectins have emerged as glycoproteins with a very interesting set of properties generally involving adhesion of cells to...