Effusion of fluid between the pigment epithelium and the retina causes a retinal detachment without retinal breaks. This condition may occur as a result of certain known diseases such as choroidal tumor, extensive chorioretinitis, or severe disturbances of the cardiorenal system. The present series of papers deals with a specific type of uveal effusion of unknown cause which forms a definite clinical entity. As far as is known, this condition has not been clearly recognized in the past. The present paper describes findings in 17 patients seen during the past nine years either at the Retina Service of the Massachusetts Eye and Ear Infirmary or in the offices of Retina Associates. The following clinical picture has been outlined on the basis of observations made in these cases. The disease affects almost exclusively males and causes slowly progressive and often bilateral retinal detachment, with shifting subretinal fluid and without retinal breaks.