To enable cells to crawl, adhesion receptors such as integrins most bind to extracellular molecules and simultaneously interact with force-generating components of the cytoskeleton(1,2). We show here that the binding of extracellular ligand in living cells induces the attachment of beta 1 integrins to the retrograde-snoring cytoskeleton, Unliganded integrins are not associated with the rearward-moving cytoskeleton : gold particles attached to beta 1 integrin by a monoclonal antibody diffuse inn the membrane, However, addition of soluble RGD peptide (single-letter amino-acid code) or the use of fibronectin-coated gold particles causes the attachment of integrins to the rearward-moving cytoskeleton. Deletion of the beta 1 cytoplasmic tail blocks cytoskeletal attachment. The directed movement of integrins in response to ligand indicates that ligand binding is the critical step in regulating organized receptor movement on the cell surface and the migration of adherent cells.