Thirty-six young healthy patients developed a peculiar clinical syndrome affecting only one eye. The early stage of the disease was characterized by visual loss, vitritis, mild papilledema, and successive crops of multiple, evanescent, gray-white, deep, retinal lesions. Over a period of many months there developed widespread, diffuse and focal depigmentation of the pigment epithelium, retinal arterial narrowing, optic atrophy, severe visual loss, and electroretinographic changes. A motile, subretinal round worm, probably a Toxocara, was observed in two patients.