A method suited to the study of gait is described in which the walking subject is filmed from the front and from the sides. Triangulation techniques are used in obtaining measurements from the films, projected on a special viewer. These include flexion and extension of the knee and ankle in the sagittal plane, and rotation of the pelvis, femur, and foot in the transverse plane. Exacting technique is required, and extraction of the data is somewhat time-consuming. The advantages of the method are that (1) no encumbering apparatus is attached to the patient, (2) multiple measurements may be made in a single recording session, (3) the method is painless and does not involve any discomfort for the patient, (4) electromyograms may be superimposed on the motion picture film for simultaneous recording, and (5) recordings of both extremities can be made at the same time.