Choroideremia is a bilateral, hereditary, progressive degeneration of the choroid and retina, characterized by night blindness, visual field constriction, and eventual blindness. This report summarizes the pertinent literature on this subject, calls special attention to the well-documented, asymptomatic, but detectable, carrier state, and emphasizes the need for its early diagnosis to provide prompt, appropriate genetic counseling. A family with classical choroideremia is presented to illustrate important diagnostic features of the condition and its carrier state. Historical Review In 1872, Mauthner1described two patients with pigmentary changes in the fundus, night blindness, and constricted fields; he considered this syndrome different from retinitis pigmentosa. This conclusion was based on the striking fundus features: complete atrophy of the choroid, normal retinal vessels, and absence of optic nerve atrophy. He stressed the similarity to choroidal coloboma and described it as "choroideremia," which implied a developmental or congenital absence of the choroid. As cases accumulated,