A 6-month old girl had unilateral leukokoria. Because retinoblastoma could not be excluded, the blind left eye was enucleated. Histopathologically, a total retinal detachment associated with a widespread cavernous hemangioma of the retina and a preretinal membrane were found. The specimen was further examined by immunohistochemistry and electron microscopy to determine the origin of the preretinal membrane and to study the anatomy of the telangiectatic retinal vessels. The preretinal membrane was mostly composed of spindle-shaped cells that demonstrated immunohistochemically the presence of glial fibrillary-acidic protein and showed, ultrastructurally, numerous glial filaments in their cytoplasm. These findings support the view that this membrane was of glial origin. By electron microscopy, the telangiectatic retinal vessels displayed the anatomic features normally encountered in retinal vessels, which accounts for the absence of exudates observed clinically and angiographically in cases of cavernous hemangioma of the retina.