In a survey for coronary risk factors 14 667 adult men and women answered a questionnaire on lifestyle, diet, and health, including whether they had psoriasis. The overall prevalence of psoriasis was 4.79% in men and 4.85% in women. The data showed an increasing incidence of psoriasis. The association with family history, lifestyle, diet, and health was explored by multiple regression analysis. The occurrence of psoriasis in first degree relatives contributed to more than 90% of the explained variance for both sexes. Of the other variables, only the positive association with rheumatoid arthritis was significant in both sexes. It is concluded that the examined environmental factors have only minor effects on the prevalence of psoriasis.