Over the past several years we have been impressed by the large number of presentations at meetings and reports in scientific journals describing the use of intravitreal silicone oil for the treatment of complicated retinal detachments. Judging by the number of such presentations and reports, one might assume that silicone oil is of proven efficacy in the treatment of proliferative vitreoretinopathy and other retinal disorders. Indeed, in many parts of the world, silicone oil has become part of the standard care for various types of retinal detachments. Unfortunately, in spite of the extensive experience accumulated regarding the use of intravitreal silicone oil, major uncertainties have guided the Food and Drug Administration in its decision to require further clinical testing before approving silicone oil for general use within the eye. To aid the accumulation of necessary data regarding the safety and efficacy of intravitreal silicone oil, the National Eye Institute is