Men and nonpregnant women between ages 18 and 49 years with common forms of RP were included. All eligible patients had retinal arteriolar attenuation, elevated dark adaptation thresholds, and reduced ERGs. Patients had best corrected Snellen visual acuity of 20/100 or better, central visual field diameter on the Goldman perimeter with V4 e white test light of 8 degrees or greater, and ERG amplitude of 2.5 or greater in response to 0.5-Hz white light or of 0.12 ultraviolet light or greater in response to 30-Hz white flickering light in at least one eye. In addition, patients had normal fasting serum retinol and serum liver function profile and weight above the lower fifth percentile for age, sex, and height. All patients had a total estimated pre-trial intake of vitamins A and E from diet plus pills not greater than 11,500 IU/day and 40 IU/day, respectively.