In four Norwegian counties (fylker) 89 probands with tapeto-retinal degeneration have been traced and examined by the author. 407 of their nearest relatives (mostly first degree relatives) were also examined. A total of 63 of the relatives were found to be affected, of whom 42 had not been registered previously. After completion of the examinations the mode of inheritance differed from that previously estimated in 50% of the families. Of the 48 families with "classical" retinitis pigmentosa, 8% showed autosomal dominant, 50% autosomal recessive and 2% X-linked recessive inheritance. The remaining 40% were families with solitary cases without consanguinity between the parents of the affected person. Of five families with retinitis pigmentosa of pericentral type, four demonstrated an autosomal dominant pattern of inheritance.