The past years have seen considerable progress in the characterization of hereditary factors in primary open-angle glaucoma. Epidemiologic studies strengthened our knowledge of the hereditary factors in this multifactorial disease. Several loci in the human genome have been described, which segregate with different glaucoma phenotypes. Mutations of the MYOC/TIGR (myocilin/trabecular meshwork inducible glucocorticoid response) gene on chromosome 1q account for most, but probably not all, cases of glaucoma linked to chromosome 1q, and other additional pathologic factors may be implicated. The properties of the normal myocilin protein point to a crucial role in the regulation of intraocular pressure. However, in spite of the knowledge obtained so far, routinely performed genetic screening of patients at risk for primary open-angle glaucoma is not yet clinically useful.