The method of timing for short sprints has recently come under closer scrutiny. While most studies show hand-timing to be significantly faster than electronic timing, the degree of the differential between the two methods remains controversial. The purpose of this study was to determine the source of timing differentials between hand-timing and electronic-timing systems in the 40-yd dash. Twenty-seven male college-aged volunteers (Wt = 82.8 ± 9.3 kg) ran two 40-yd dashes on an indoor rubberized floor. A computerized electronic data collection system recorded numerous temporal events; runner's hand start pad (EHSP), runner's foot start pad (EFSP) and stop time event from a photocell beam placed at a height of 0.75m for each runner. This same system recorded start and stop events from hand-held stopwatch buttons operated by 6 hand-timers who were instructed to initiate timing on the first visible movement of the runner. The differential times were calculated with EFSP as the zero time. Electronic start events were not significantly different (p = 1.0), with EHSP being (M ± SE) 0.001 ± 0.014s slower than EFSP. Hand-timing was initiated significantly slower (0.065 ± 0.017s, p<0.001) than EFSP. The average hand-stopping time was significantly faster (0.160 ± 0.043s) than electronic stop time. When the differential for start and finish times were combined, they produce significantly faster 40- yd dash times (0.225 ± 0.024s, p<0.001) with hand-timing (5.23 ± 0.037s) than with electronic timing (5.45 ± 0.051s). Hand-timed 40-yd dashes will likely be 3.99 ± 0.38% faster than electronic timing. The discrepancy is due to a combination of start and finish differentials in timing. When short-sprint timing is an important element in judging performance or is to be used as a measure of training improvement, electronic timing may provide a more valid and reliable approach.