We observed 12(35.3%) cases of subretinal membranes in 34 patients with long-standing retinal detachments with proliferative vitreoretinopathy. Transmission electron microscopy revealed that glial cells, retinal pigment epithelial cells and a great amount of collagen represented the basic cellular and substantial components in a subretinal membrane obtained by vitreous surgery. （Chin J Ocul Fundus Dis,1994,10:165-166）