In order to investigate the efficacy of repeated irradiation of low-power helium-neon laser in pain relief, we irradiated 36 outpatients suffering from postherpetic neuralgia. Each patient underwent 20 trials of irradiation on several points around the painful area at a frequency of 2 or 3 times a week. The efficacy of the laser at the end of 20 trials was noticed on 88.9%, and the degree of pain relief was 55.3%, which correlated with the number of trials. These results suggest that the irradiation of He-Ne laser is an effective and safe treatment for postherpetic neuralgia.