1. The retinal periphery was explored with binocular indirect ophthalmoscopy and scleral depression in members of the families of patients with detachment due to retinal disinsertions and 30 pedigrees have been thus obtained. 2. A genetic causation of this disease is postulated, based in the concentration of cases in some of the sibships studied (33% of the sibships with 2 or more siblings); furthermore, the disease was demonstrated in two identical twins and was absent in two fraternal twins. 3. The sex incidence was similar and the vast majority of affected individuals had normal parents, suggesting an autosomal recessive mode of inheritance for at least some of the cases.