Leber's hereditary optic neuropathy (LHON) is a maternally inherited disease characterized of acute visual loss predominantly affecting young men. So far twelve mutations in the mitochondrial DNA have been associated in this disease. We reviewed these mutations, and showed methods to detect these mutations which are being used in our laboratory. Seven mutations (nps 3460, 5244, 7444, 11778, 13708, 15257, 15812) can be detected by the the loss of the sites, and 4 mutations (nps 4216, 4917, 11778, 3394) can be detected by the appearance of the restriction sites. Since only two mutations (nps 4160 and 14484) don't affect the restriction sites, we use mismatched primers as a method to detect the mutations by polymerase chain reaction.