Information on prevalence of psoriasis was obtained from a health interview survey conducted by Central Bureau of Statistics of Norway in 1985 of a representative sample of the Norwegian population. Altogether 149 cases of psoriasis were registered in the study population of 10,576 persons, giving an overall prevalence of 1.4%, with no difference between males and females. A peak prevalence was observed in the age group 30-49 years, and a significantly lower prevalence of 0.5% was found in Hedmark and Oppland counties, as compared with the country as a whole. A higher prevalence of psoriasis among females was found in urban vis-à-vis rural areas, and in urban areas, the prevalence was higher for females than for males. No difference in prevalence was found between various socio-economic groups.