That heredity plays a role in so-called spontaneous idiopathic detachment of the retina has been known for a long time. As early as 1885 Lang submitted a family in which brother and sister were afflicted. A collected account of the problem was not, however, published until 1936 when R i c h e r reported on 36 families with retinal detachment. In the course of time, authors from a number of different countries have reported on single families with inherited cases. In Denmark, Brendstrup (1941) has submitted 5 cases occurring in 2 families. According to Frangois the heredity is generally recessive, but cases of irregular autosomal dominance have been reported (Waardenburg), and in one family sex-linked dominance (Vogt). In the great majority of cases the disease has been found in families and in individuals with severe or excessive myopia. A few cases of familial retinal detachment in non-myopic persons have been reported by Zur Nedden and Frangois. The relationship between myopia and retinal detachment is generally known, although the number of cases occurring in non-myopic subjects appears to be on the increase. The infantile traumatic cases and in particular the senile degenerative cases usually belong to this group of non-myopic cases. Myopic retinal detachment, on the other hand, appears to occur in younger adults, between 30 and 50. Spontaneous retinal detachment appears to be caused by certain degenerative changes of the eyeground occurring with particular frequency in myopia. These myopic retinal changes do not differ from ordinary senile degeneration; only, they occur at an earlier age (Vogt). Myopia thus favours retinal detachment which, however, does not differ from other forms of retinal detachment. Vontobel demonstrated that the degenerations do not occur until the myopia has stopped progressing. H e advanced the view that the retinal changes are not due to mechanical causes related to the myopia, but to a special inherited trait. This has been confirmed in studies on mono-