This study is a randomized, controlled, double-masked trial with a planned duration of 5 years. Patients with the common forms of RP are assigned to either a test or a control group. All receive 15,000 IU/day of vitamin A palmitate in addition to the capsules under study. Participants will not know the contents of the supplement or the group to which they have been assigned until the end of the trial. The main outcome measurement is the total point score on the Humphrey Field Analyzer (HFA). In addition, computer-averaged 30-Hz cone ERG amplitudes and visual acuity are measured annually.