Genetic factors have long been implicated in the pathophysiology of primary open-angle glaucoma (POAG). Recently, myocilin, a gene of unknown function, was associated with both juvenile open-angle glaucoma (JOAG) and POAG. Forty-three different myocilin mutations have been reported in open-angle glaucoma patients, and several large studies have suggested that as a group these mutations are associated with 3-4% of POAG in patient populations worldwide. Support for the pathogenicity of the individual myocilin mutations has been obtained from in vitro assays, statistical methods, and conservation of gene sequence arguments. Several of these myocilin mutations were observed in multiple patients allowing the identification of mutation-specific glaucoma phenotypes (maximum intraocular pressure and age at diagnosis). Associations between myocilin and other forms of open-angle glaucoma have been explored. At present there is no evidence to link myocilin mutations and steroid-induced ocular hypertension or normal-tension glaucoma. Clinical vignettes of POAG patients from four generations of a family harboring the TYR437HIS myocilin mutation are presented, highlighting the benefits of elucidating the genetics of glaucoma.