The purpose of the research was to determine the variability of selected parameters during the support phase of running between consecutive right footfalls, and the included left footfall, as well as to acquire additional descriptive data on lower extremity function. Eleven college aged male runners were filmed (200 fps) from the rear and side while running on a treadmill at 4.29--4.47 m/sec. The statistical analysis of the mean absolute differences for temporal events between the three footfalls resulted in no significant differences. An estimate of event variability was calculated to be the actual time +/- 0.0110 sec or the percentage +/- 4.98% at the 95% confidence interval. Comparisons between the absolute deviations of selected body part positions and/or orientations for the test conditions resulted in no statistically significant differences. Estimates of variability ranging from 1.78--4.08 deg were calculated. Even though no statistically significant differences were obtained, the magnitude of the variability obtained for the parameters evaluated would seem to indicate a need for calculating representative or average values if subtle differences in lower extremity function are to be detected.