A Nordic study group, NORDSYN, consisting of ophthalmologists from Denmark (Thomas Rosenberg), Finland (Sirkka-Liisa Rudanko), Iceland (Gudmundur Viggosson), Norway (Tor Flage, Egill Hansen, Ruth Riise) and Sweden (Kristina Tornqvist), has compiled data from registers in Denmark, Finland, Iceland and Norway of 2527 visually impaired children. The Swedish register was established later in 1990. Each record contains the following information: sex, year of birth, year of registration, classification of visual impairment, ocular diagnosis, systemic diagnosis, aetiology and evt. additional impairments. The ocular diagnoses were compiled into groups among which congenital malformations and neuro-ophthalmological diseases were the most dominating. A coding system for aetiology was developed. It was demonstrated, that prenatal factors, including genetic aetiologies, were involved in a large proportion (66%) of the cases. The sex distribution revealed a dominance of males compared to the general population at the same age. The age-specific national prevalences for registration of childhood blindness (WHO-definition: best corrected visual acuity in the best eye less than 3/60 or visual field less than 10 degrees around fixation for the ages 0-15 years) were (N/100,000): Denmark 41, Finland 15, Iceland 19 and Norway 15. The differences were primarily presumed to be due to varying efficiency in registration. A coding system for additional impairments was developed. The proportion of visually impaired children with an additional mobility, hearing or mental impairment was between one third and one half of the national materials thus indicating the need for interdisciplinary tracing of and care for the visually impaired child.