Males with a clinical diagnosis of X-linked retinitis pigmentosa (XLRP) caused by RPGR-ORF15 mutations will be asked to provide informed consent and will have a single blood or saliva sample obtained for DNA sequence analysis of genes known to cause XLRP, including the RPGR-ORF15 gene. All participants will be informed of the results of testing for these mutations. Those with qualifying mutations in the RPGR-ORF15 gene will be evaluated every 6 months for 3 years using a variety of non-invasive visual function tests to more fully characterize their clinical condition. Testing will include routine ophthalmic examinations and tests of visual acuity, perimetry, OCT, fundus imaging, and completion of quality of life questionnaires.