The effects of speed and gradient on stereotyped pattern of temporal-distance parameters of the lower limb in human gait were observed on five male subjects walking on a treadmill.Step length and step duration were consecutively determined by means of a computerized system.Step lengrt hincreased approximately in proportion to the square root of the speed,and step duration decreased in proportion to the reciprocal of the square root of the speed.In grade waiking,when compared with level walking,the subject had a tendency to take shorter steps at high speeds and longer steps at low speeds.Standard deviations of step length and step duration showed the minima at the speeds which were estimated to be about 90 and 95m/min for step length and step duration,respectively,although there were some variations of the speed with gradient.Coefficients of variation of these factors also showed the minima at particular speeds.These results suggest that when the subject is allowed to choose his own step length,there exists the speed at which the fluctuation of stereotyped movement of lower limb shows the minimum.