IN THIS communication the mode of action of cyclodialysis is interpreted on the basis of histologic observations in 2 eyes operated on for chronic glaucoma. Tension was successfully normalized by cyclodialysis and remained so from the time of operation until the patient's death, fifteen months later. Gonioscopic findings in similar cases are coordinated in the study, and certain surgical conclusions are drawn. Heretofore, histologic examination of eyes treated by cyclodialysis has been performed only in cases in which the operation failed, with 1 exception. This was an eye operated on by Elsching1 in which tension was normalized for fifteen years, from the date of operation until the patient's death. The upper inner part of the anterior chamber (untouched by the cyclodialysis spatula) showed broad glaucomatous synechias of the root of the iris. Schlemm's veins were partly occluded. In the region of cyclodialysis the synechias were separated from the