A double-blind study has been performed to search for the possible effect of khellin in psoriasis. 10 patients were treated orally with khellin and subsequently exposed to sunlight for 4 months; a total of 8 cases responded positively with variable degrees of clearance. None of 10 controls had any response. A relapse-free duration of 3 years was recorded for 6 out of the 8 responders. This study would introduce the nonpsoralen compound khellin as a possible agent for the therapy of psoriasis.