Increasing experimental concern with locomotion and its neural control prompted the construction of a motor-driven treadmill for cats. The apparatus was designed for kinematic analysis of gait from 16 mm movie film, but it will also permit a variety of other records to be taken. A box, or base, houses two large drums and the belt drive. Space is provided on top of the base for a closed locomotion compartment that is transparent on the filming side. There is also sufficient space on top of the base for support apparatus, operator controls, and animal exits. Cats may be trained to work for food reward alone, as delivered from the front by the operator. Alternatively, they can be trained to stay near the front of the treadmill belt in order to avoid an aversive jet of air or electric shock, either of which can be delivered at the rear of the test chamber. The operator can maintain forward belt velocity at fixed levels between 0.5 and 6 m/sec, or he can vary velocity continuously. Displays of a tachometer and a special timing device are large enough to be clearly visible on the film. These various features in combination provide a controlled and varsatile stepping environment, in which the cat can move without physical restraints.