The design and construction of an electrogoniometer for measuring angular displacements of the hip is discussed. It has been used to measure hip movements for a number of activities, including walking, climbing and descending stairs, and standing and sitting. Data from the goniometer are recorded on magnetic tape and are then processed and printed out in graphical format by minicomputer. A large number of healthy people have been examined to establish the normal movement patterns for the various exercises. These patterns are compared with those produced by people suffering from pathological hip conditions, especially osteoarthrosis. Measurements have been made on patients who have undergone hip replacement surgery. The degeneration of the movement patterns associated with osteoarthrosis are demonstrated, as are the improvements following arthroplasty. It is intended that the goniometer be used to provide prognostic and therapeutic guidelines in the clinical environment