Seven abortive neovascular outgrowths (ANVOs) from diabetic retinas were obtained for examination either by biopsy during pars plana vitrectomy (2) or after discovery within enucleated globes (5). Scanning and electron microscopical, histochemical, immunohistochemical and retinal digest techniques were used. The ANVOs consisted of nodules of vessels without an extravascular fibrous component. Two of them contained aneurysm-like dilatations of constituent vessels, and all the specimens showed gross hyaline thickening of the vessel walls. The vascular sclerosis was probably due to accumulation of plasma proteins in the walls of the damaged vessels, which contributes to their involution seen clinically after retinal photocoagulation.