We have developed a pacing device consisting of a series of surface-mount light emitting diodes (leds) attached to a sub-mm thickness flexible-printed-circuit-board substrate. The device is sufficiently thin to be embedded in the floor-covering in a gait laboratory. Leds are illuminated in sequence to give the impression of movement and thus act as a visual cue for speed of locomotion. The ability of the system to control speed was compared to subjective instructions and a metronome for one subjective instructions and a metronome for one subject at 3 walking and 2 running speeds. The packing lights produced the smallest spread of speeds at most desired speeds and also more closely matched the cadence-speed (or stride length-speed) relationship of unconstrained walking. Other sports and medial applications of the device will be discussed.