The hereditary choroidal dystrophies are divided into (1) geographic choroidal dystrophies (central areolar, peripapillary, generalised), (2) gyrate atrophy, and (3) choroideremia. Each of these disorders is discussed with regard to mode of inheritance, age of onset, symptoms, fundus appearance, and visual function testing. A typical case history of each disorder is presented together with fluorescein angiography, and the fluorescein angiographic findings are related to our present understanding of these diseases. Fluorescein angiography was found to be most helpful in diagnosing the early cases, by confirming the absence of the choriocapillaris, and in demonstrating either a local or general abnormality. The role of fluorescein angiography in understanding the aetiology of choroidan dystrophies is discussed.