This population-based study was undertaken to obtain information on age-, sex-, and race-specific incidence of nonarteritic and arteritic anterior ischemic optic neuropathy for the State of Missouri and for Los Angeles County, California. Among subjects who were 50 or older the estimated mean annual incidence rates per 100,000 population were 2.30 for nonarteritic anterior ischemic optic neuropathy and 0.36 for arteritic anterior ischemic optic neuropathy. White individuals appear to be at significantly higher risk of developing nonarteritic anterior ischemic optic neuropathy than black or Hispanic individuals, suggesting possible genetic predisposition.