Purpose. To uncover extracellular matrix (ECM) and basement membrane (BM) alterations in retinas of diabetic retinopathy (DR) eyes. Methods. Cryostat sections of human autopsy eyes obtained from NDRI (6 normal, 5 diabetic without DR, and 12 diabetic with DR, including 7 IDDM and 5 NIDDM) were subjected to immunofluorescence with antibodies to 25 ECM and BM components. Results. Fibrotic alterations of the retinal BM, or inner limiting membrane (ILM), were found in DR retinas. Normal and non-DR diabetic ILM had laminin-4, α3-α5 type IV collagen, perlecan and entactin/nidogen. In most DR cases, ILM also stained strongly for fibronectin and types I, III, IV (α1-α2) and V collagen. In diabetic preretinal membranes (n=3), perlecan, bamacan, types VI, XII and XIV collagen were newly found. In areas of neovascularization (n=4), BMs of new blood vessels in DR retinas and preretinal membranes stained strongly for tenascin and type XII collagen. In retinal vessels of normal, diabetic and even adjacent DR retinas, only weak and irregular staining for both components could be revealed. Conclusions. Fibrotic changes of ILM in DR may lead to the isolation of retina from vitreous-derived growth inhibitors, and promote neovascularization and formation of preretinal membranes. BM changes in newly formed retinal blood vessels may reflect and/or contribute to the abnormalities of their structure (pericyte absence) and function.