INCIDENCE OF RETINAL BREAKS AND DETACHMENT IN FELLOW EYES. The fellow eyes of 226 giant retinal breaks were followed in order to determine the incidence and natural course of chorioretinal and vitreous pathology. During the period of observation which ranged from 18 months to 16 years, the incidence of retinal breaks and retinal detachment increased from 36.1 percent to 51.3 percent. By the end of the follow-up period, the incidence of bilateral giant retinal breaks was 12.8 percent; retinal tears 11.9 percent, retinal holes 10.2 percent, retinal dialysis 0.4 percent, and retinal detachment 15.9 percent. The average duration of follow-up was 3.7 years, therefore, the incidence of retinal breaks in fellow eyes is probably significantly higher. VITREORETINAL CHANGES PRECEDING THE DEVELOPMENT OF RETINAL BREAKS. Syneresis, liquefaction, and condensation of the vitreous base were observed in the majority fellow eyes that developed retinal tears or giant retinal breaks. Follow-up of fellow eyes revealed that the development of a giant retinal break is often preceded by increasing white with pressure associated with increasing condensation of the vitreous base. MANAGEMENT OF FELLOW EYES. Bcause of the high incidence of retinal breaks developing in the fellow eye, regular and thorough examination of the vitreous and retinal breaks even though the fundus may appear normal at the initial examination. PROPHYLACTIC TREATMENT. This study suggests that prophylactic treatment is beneficial in the management of fellow eyes of giant retinal breaks. During this study, retinal breaks developed in 27.3 percent of untreated eyes and in 2.4 percent of eyes treated prophylactically. PROPHYLACTIC TREATMENT OF FELLOW EYES OF GIANT RETINAL BREAKS. Its seems prudent to prophylactically treat retinal holes or dialyses in eyes without retinal detachment with cryotherapy. Scleral bucking seems justified in the prophylactic treatment of eyes with retinal tears of lattice-like degeneration with retinal breaks or highly myopic eyes with increasing white with pressure and increasing condensation of the vitreous base.