We found that the action spectrum for retinal damage (determined by the fundus photographic appearance of a minimal lesion immediately after exposure) extends into the near-ultraviolet by exposing three aphakic eyes from rhesus monkeys to 405-, 380-, 350-, and 320-nm wavelengths produced by a 2,500-W xenon lamp equipped with quartz optics and 10-nm interference filters. Exposure times were 100 and 1,000 seconds and the spot diameter on the retina was 500 micrometers. The retina was six times more sensitive to 350- and 325-nm wavelengths than to blue light (441 nm). Both ophthalmoscopic and histologic data showed that near-ultraviolet lesions differed in important respects from blue-light lesions. Near-ultraviolet produced irreparable damage to rod and cone photoreceptors.