CYCLODIALYSIS as an operation for the relief of increased intraocular pressure has gained in favor with the staff of the ophthalmologic clinic at the University of Iowa until at present it is our operation of choice for chronic noncongestive wide angle or narrow angle glaucoma, hydrophthalmos and certain types of secondary glaucoma, notably that after cataract extraction. This paper is a report on the results of 100 consecutive operations made, with one exception, on patients with chronic primary glaucoma and followed for at least one year. The literature on this operation has been covered thoroughly in the excellent reviews of Salus1 in 1920 and Sugar2 in 1947. Apparently, the first attempt to create an opening between the anterior chamber and the suprachoroidal space was reported by Querenghi3 almost fifty years ago. However, Heine4 (1905) devised the operation now known as cyclodialysis. The purpose of each of