We used electron microscopy and light-microscopic immunohistochemistry of cellular and extracellular markers to characterize the cellular and extracellular components of 15 surgically resected idiopathic epiretinal membranes (IEMs). Ten specimens from the eyes with posterior vitreous detachment (PVD) consisted of inner limiting membrane, collagen layer and a flattened cell layer. Six out of the 10 specimens were also examined immunohistochemically, and fibronectin and type I, II, III and IV collagens were identified in a characteristic lamellar construct in the IEMs. On the other hand, 5 specimens obtained from the eyes without PVD consisted mainly of a thick layer of collagen fibrils with or without a flattened cell layer. Two of the 5 specimens were also examined immunohistochemically, and the collagen fibrils in the specimens were identified as type II collagen. Glial cells (glial fibrillary acidic protein-immunoreactive cells) were also identified in 3 specimens. These results indicate that there are some variations in the IEMs.