A double-blind study of the effect of 6-azauridine triacetate (azaribine) in psoriasis was conducted. One group received azaribine in a dose of 200 mg/kg of body weight per day for 6 weeks. The second group received placebo. Patients who failed to improve or relapsed were switched to the other group (studies A and B). Responses were judged as follows: excellent (complete clearing of lesions), good (75% reduction in size and thickness of lesions), fair (50% reduction in size and thickness of lesions), no improvement, and worse. After the double-blind study 11 patients were treated with azaribine in a dose of 100 mg/kg of body weight per day for 12 weeks (study C). Nine were then treated with optimal dose (study D). Twenty-two patients completed studies A and B. The responses to azaribine were 5, excellent; 11, good; 2, fair; 1, no improvement; and 3, worse. The responses to placebo were 0, excellent; 2, good; 2, fair; 1 no improvement; and 17, worse. The responses in study C were 1, excellent; 7, good; and 3, fair; and in study D there were 7 good and 2 fair. Mild marrow depression was the only toxicity observed.