The invention relates to a regulating valve, which is attachable in particular in a bore, executed with a female thread, of a hydraulic door closer. The regulating valve has a body adjoined by a regulating area. The regulating valve also has a thread provided with an anti-rotation element. The thread, including the anti-rotation element, being screwed into the female thread of the bore. In order to provide a regulating valve of a simple design, in which any unwanted adjustment of the regulating valve during operation is excluded, the anti-rotation element of the regulating valve has a plastic material layer at the thread flanks of the thread. The plastic material layer cooperates with the female thread of the door closer.