• Diffuse unilateral subacute neuroretinitis is an endemic disease associated with severe visual loss in the south-eastern and midwestern United States and the Caribbean. It is caused by a single nematode that may wander in the subretinal space for many months or years. Until recently, the only effective treatment has involved the difficult and time-consuming biomicroscopic detection of the worm followed by photocoagulation. This report describes the use of oral thiabendazole in four patients with presumed diffuse, unilateral, subacute neuroretinitis. Serial fundus photography was used to detect evidence of early destruction of the worm.