This study reports on the novel use of a portable system to measure gait cycle parameters. Measurements were made by a triaxial accelerometer over the lower trunk during timed walking over a range of self-administered speeds. Signals from each trial were transformed to a horizontal-vertical coordinate system and analyzed by an unbiased autocorrelation procedure to obtain cadence, step length, and measures of gait regularity and symmetry. By curvilinear interpolation, speed-dependent gait parameters could be compared at a normalized speed. It was demonstrated that analysis of gait cycle parameters which previously required fixed laboratory equipment and paced walking procedures, now can be made from data obtained by a timing device and a portable sensor at free walking speeds.