Neovascular glaucoma, as a typical secondary glaucoma, is due to ocular or (earlier) systemic diseases. The formation of a fibrovascular membrane on the anterior surface of the iris (rubeosis iridis) and extending into the chamber angle leads to irreversible obliteration of the outflow system, with a corresponding rise in intraocular pressure. The most frequent cause is retinal ischaemia resulting either from vascular occlusion or from diabetic alterations. The differential diagnosis must include acute angle-closure glaucoma and uncontrolled open-angle glaucoma. Treatment is aimed at eliminating the actual cause or at least reducing the risk factors (e.g. by retinal laser coagulation), or consists in cyclodestructive procedures. Medicamentous therapy comprises anti-inflammatory agents (steroids, cycloplegic agents) and substances that reduce the production of aqueous humour (carbonic anhydrase antagonists, beta blockers). In the near future, antiangiogenic medication might be another effective option. For end-stage neovascular glaucoma, the implantation of drainage devices is also discussed.