The heritable falciform folds and congenital retinal non-attachment reported in the literature are here divided into monosymptomatic and complex types. Of the former, autosomal dominant and recessive disorders are known. The complex types comprise several syndromes, both autosomal recessive and X-linked. Retinal dysplasia is sometimes seen in histological sections from these affections, but it is an unspecific histological reaction, and not a disease sui generis. Attention is drawn to the syndrome with microcephaly, microphthalmia and falciform detachment which, though previously described, has not so far been delineated. It is hypothesized that hydrocephaly and congenital retinal non-attachment with or without microphthalmia and persistent hyperplastic primary vitreous constitute yet another 'new' syndrome, mainly seen in females.