Abstract: The invention relates to a device for positioning and guiding a surgical instrument during orthopaedic interventions, comprising an industrial robot which has a program-controlled robot arm (1) with several articulated joints and a mounting plate (2) at the end of said arm, an instrument (3) for the orthopaedic intervention attached to the mounting plate (2) and a program control with computer. Sensors for detecting the position of the joints in an instrument-coordinating system defined in the program control are situated in the joints of the robot arm (1). According to the invention, a manually guided sensor device, for example in the form of a sensor arm (4) with multiple joints, is used for the three-dimensional measurement of an object by the instrument-coordinating system of the industrial robot. Using the sensor device (4), and with a previously adopted basic position of the robot arm (1) specified by the program control, reference points can be detected on the bone of the patient.