Leber Hereditary Optic Neuropathy is a maternally inherited condition that is characterized by acute or subacute bilateral loss of vision, usually in otherwise healthy young individuals. Several point mutations in the mitochondrial genome have been identified in patients with the condition. Scientific advances into a better understanding of the molecular pathogenesis have been hampered by the lack of an animal model for the disease. This article summarizes what is known about the clinical features, epidemiology and genetics of Leber Hereditary Optic Neuropathy and reviews recent experiments scientists have used in addressing the many unanswered questions that remain about the disease.