In a randomized, double-blind comparative study 60 patients with severe, widespread psoriasis were treated either with photochemotherapy (PUVA) alone or in combination with acitretin. Forty-eight patients completed the study; of these, 25 received placebo combined with PUVA and 23 received acitretin with PUVA. Marked or complete clearing of psoriasis occurred in 80% of the patients (20 of 25) without acitretin and in 96% of the patients (22 of 23) with adjunctive acitretin administration. The mean cumulative UVA dose given to patients in the acitretin-PUVA group was 42% less than that required for patients in the placebo-PUVA group. We conclude that acitretin substantially augments the efficacy of photochemotherapy in the treatment of severe psoriasis.