The distribution of fibronectin and laminin in diabetic human eyes was determined by indirect immunofluorescent techniques. The intense fluorescence suggests increased amounts of fibronectin and laminin in the diabetic internal limiting membrane (ILM). A double laminated pattern of fluorescence for both glycoproteins suggests structural abnormalities of the ILM of the posterior retina. Preretinal and subretinal proliferative tissues fluoresced strongly and diffusely with antifibronectin. This study indicates that in diabetic patients, the ILM, especially in the posterior retina, is biochemically and morphologically abnormal.