To investigate causes of blindness in childhood, 776 children (infancy to 20 years old) in special schools were seen in 1963. Examinations, parent questionnaires, and correspondence with health personnel were used to obtain etiological data. Causes of blindness mainly of genetic determination described are choroido-retinal degenerations, retinoblastoma, pseudoglioma and retinal detachment, optic atrophy, congenital and infantile cataracts, myopia, lesions of the cornea, coloboma, microphthalmos, anophthalmos, aniridia, buphthalmos, blindness as part of a syndrome involving other malformations, and blindness secondary to malformations. Prenatally acquired blindness, retrolental fibroplasia, blindness acquired in infancy or childhood, and conclusions about the research findings and limitations are discussed. Appendixes present the parent questionnaire and data concerning the children with each condition. (RP)