This paper presents the results obtained in 38 eyes treated by cyclodiathermy using a technique described by Reiser * in 1949, and observed by us in Castroviejo's clinic in 1950. Tonographic studies were done postoperatively on 13 eyes in an attempt to gain some knowledge regarding the mechanism of action of this type of operation. An evaluation of cyclodiathermy seems appropriate at this time because the operation is experiencing a second peak of popularity, the first having occurred as a result of Vogt's † work in 1936. After his reports cyclodiathermy was widely used, but after a few years it fell into relative disrepute in this country. Vogt's original method utilized as many as 100 punctures placed in parallel rows, beginning 2.5 mm. behind the limbus, over an area of the sclera extending one-third to one-half the circumference of the globe and reaching as far posteriorly as the insertions of the