The purpose of this randomized, double-blind study was to determine the effect of a helium-neon (He-Ne) laser on latency of peripheral sensory nerve. Forty healthy subjects with no history of right upper extremity pathological conditions were assigned to either a Laser or a Placebo Group. Six 1-cm2 blocks along a 12-cm segment of the subjects' right superficial radial nerve received 20-second applications of either the He-Ne laser or a placebo. We assessed differences between pretest and posttest latencies with t tests for correlated and independent samples. The Laser Group showed a statistically significant increase in latency that corresponded to a decrease in sensory nerve conduction velocity. Short-duration He-Ne laser application significantly increased the distal latency of the superficial radial nerve. This finding provides information about the mechanism of the reported pain-relieving effect of the He-Ne laser.