Eight cases of the plateau iris syndrome are presented. The "plateau iris syndrome" should be differentiated from the "plateau iris configuration." The "configuration" refers to a preoperative condition in which gonioscopically confirmed angle-closure glaucoma occurs, but the iris plane is flat and the anterior chamber is not shallow axially. In most cases, the angle-closure glaucoma associated with the plateau iris configuration is cured by a peripheral iridectomy. "Plateau iris syndrome" refers to a postoperative condition in which a patent iridectomy has removed the relative pupillary block which is ordinarily important in causing angle closure, but gonioscopically confirmed angle closure recurs without shallowing of the anterior chamber axially. Plateau iris syndrome is rare compared to the configuration, which itself is not common. In the syndrome, angle closure usually occurs in the early postoperative period but may occur long after iridectomy when the pupil dilates spontaneously or in response to mydriatic agents. It usually occurs in a younger age group than ordinary angle-closure glaucoma. The treatment is the use of pilocarpine postoperatively as long as it is needed. This syndrome must be considered in the differential diagnosis when the intraocular pressure rises unexpectedly following an adequate peripheral iridectomy procedure for angle-closure glaucoma.