Abstract: A rotor blade pitch adjustment device for a wind power installation includes a motor/pump unit whose rotation speed and direction are variable and which is connected for fluid-flow purposes to a hydraulic actuator via a hydraulic open-loop/closed-loop control system. The actuator is mechanically coupled to at least one rotor blade of the wind power installation in order to rotate the rotor blade about its longitudinal axis. An electrical control circuit, which comprises an emergency power supply device, is provided for operation of the motor.