PURPOSE. To map the gene(s) associated with autosomal dominant (AD) high-grade myopia. METHODS. A multigeneration English/Canadian family with AD severe myopia was ascertained. Myopes were healthy, with no clinical evidence of syndromic disease, anterior segment abnormalities, or glaucoma. The family contained 22 participating members (12 affected). The average age of diagnosis of myopia was 8.9 years (range, birth to 11 years). The average refractive error for affected adults was -13.925 D (range, -5.50 to -50.00). Microsatellite markers for genotyping were used to assess linkage to several candidate loci, including three previously identified AD high-myopia loci on 18p11.31, 12q22q23, and 7q36. Syndromic myopia linkage was excluded by using intragenic or flanking markers for Stickler syndrome types 1, 2, and 2B; Marfan syndrome; Ehlers-Danlos syndrome type 4; and juvenile glaucoma. A full genome screening was performed, with 327 microsatellite markers spaced by 5 to 10 cM. Two-point linkage was analyzed using the FASTLINK program run at 90% penetrance and a myopia gene frequency of 0.0133. RESULTS. Linkage to all candidate loci was excluded. The genome screening yielded a maximum two-point lod score of 3.17 at θ = 0 with microsatellite marker D17S1604. Fine mapping and haplotype analysis defined the critical interval of 7.71 cM at 17q21-22. CONCLUSIONS. A novel putative disease locus for AD high-grade myopia has been identified and provides additional support for genetic heterogeneity for this disorder.