UVB radiation is beneficial for the treatment of psoriasis vulgaris. Patients with recalcitrant disease, however, are slow to respond to UVB phototherapy with and without the use of coal tars or emollients. Etretinate and, more recently, acitretin have proved useful, but clinical improvement is slow when they are used as monotherapy in plaque psoriasis. Each drug also produces side effects, some of which are dose related. This study was designed to compare results of treatment with UVB combined with either acitretin (50 mg/day) or placebo to determine if psoriasis would respond faster and to less cumulative exposure to UVB and acitretin. The psoriatic disease cleared to a greater degree in patients treated with acitretin-UVB with fewer treatments and smaller amounts of UVB radiation than in patients treated with either placebo-UVB or acitretin alone.