Abstract: A back pressure regulator system is set forth. In the preferred embodiment, a pressure to be regulated is input to a pressure transducer. The transducer forms a signal indicative of pressure applied through a regulator system which forms an output driving differential signal suitable for a motor. An electric motor is driven thereby and operates a gear box which in turn connects through a slip clutch and a linear motion clutch to advance or retract a needle valve stem. The stem is threadedly engaged with the body. It rotates to advance or retract a needle valve in a valve seat, and a connection is made from the pressure to be regulated through the needle valve to thereby control back presssure on the system.