It has long been suspected that genetic factors play a role in open-angle glaucoma. Only recently, however, has the molecular basis of such factors begun to be established, with the primary localization of the GLC1A locus for juvenile-onset and early-onset autosomal dominant open-angle glaucoma on chromosome 1q. These findings are clinically significant in that they allow familial screening of individuals at risk for glaucoma before the onset of irreversible visual impairment. A physical map of the GLC1A genomic region is now available, and the actual GLC1A gene might be identified in the near future. Nevertheless, open-angle glaucoma is a genetically heterogeneous entity, and additional loci have been mapped or proposed. Identification of open-angle glaucoma genes should provide invaluable clues to the disorder's pathophysiology. It could also aid in conceiving novel therapeutic agents and broadening the screening of at-risk subjects.