An anatomical taxonomy for neovascular proliferation of the optic nerve head in patients with proliferative diabetic retinopathy is presented. The technique consists in comparing (A) number of involved quadrants, (B) calibre of vessels, (C) neovascular density, (D) neovascular area, (E) plane of proliferation, and (F) fluorescein angiographic findings. A similar taxonomy is used to describe fibrous tissue proliferation at the disc. With these criteria a series of standard photographs have been utilised in a numerical grading system. This system has proved useful in documenting the natural history and response to photocoagulation therapy for diabetic disc neovascularisation.