Abstract: In an infusion set having a container for fluid medicines, which by a feed-line and a differential pressure valve is connected to a drip chamber and which by a further feed-line is connected to a front end controlled with a roller clamp according to U.S. patent application Ser. No. 08/800,779, the differential pressure valve has two inlets each with an associated differential force chamber and the two differential force chambers are sealingly separated from each other by a diaphragm disk, wherein both differential force chambers are connected to an exit line for the fluid medicine. To use the differential pressure valve, the valve is configured as a 3-way check valve by the fact that the first inlet is connected to the container for the fluid medicine and that the second inlet is designed for the connection to a syringe or the like.