The Orinda Longitudinal Study of Myopia (OLSM) was started in 1989 to investigate normal eye growth and the development of myopia in over 1,200 school-aged children to date. Beginning in 1997, three parallel study phases are being conducted. Phase 1 investigates additional factors that may predict the onset of juvenile myopia (accommodative function, peripheral refractive error, intraocular pressure, and school achievement). Phase 2 compares and contrasts the optical ocular components and refractive error profiles of other ethnic groups with the predominantly Caucasian Orinda database. Phase 3 conducts DNA-based studies on the prevalent OLSM myopes and their families to use these phenotypically well-characterized children and a panel of candidate genes to look for evidence of genetic factors. In parallel with the candidate gene association, family material is used in an allele sharing approach to identify loci using highly variable, PCR-based markers.