Interrupted-light photography was used to record the simultaneous displacement patterns of multiple body segments of 44 patients with parkinsonism during free-speed and fast walking to quantitatively characterize their gait peculiarities. The patients were categorized into three disability groups according to their independence in activities of daily living. Their measurements of walking performance were compared to those of normal men. The gait components of the patients, which related systematically to the degree of disability, were: step lengths, vertical excursions of the head, extension of the hip and knee of the backward-directed limb at the onset of contralateral weight bearing, toe-floor distance at the onset of weight bearing, and rotation of the thorax.