The ligand‐induced phosphorylation of the platelet‐derived growth factor (PDGF) receptor was followed at 37°C by a rapid dephosphorylation which was roughly parallel to the down regulation of the 125I‐PDGF binding sites. At 4°C, when the ligand‐receptor complexes remain associated with the cell surface, the phosphorylated form of the receptor was more stable. However if the ligand was dissociated from the receptor by means of a mild acid wash or a treatment with suramin, the dephosphorylation of the receptor also occurred at a low temperature. These data suggest that, due to the dissociation of the ligand, the kinase activity of the receptor is switched off so that the phosphotyrosine‐containing receptors remain exposed to the action of phosphatases that rapidly dephosphorylate them.