Ammonia is now frequently used in armed robberies by assailants, who possibly misguidedly imagine that it is an easy and safe method of temporarily incapacitating their victim. Nevertheless, two case histories are presented to illustrate the early rise of intraocular pressure which may occur after excessive exposure of the eye to ammonia. The clinical appearance in many respects mimicked that of acute-angle closure glaucoma; the raised intraocular pressure, corneal oedema, and an oval semi-dilated fixed pupil being typical.