The purpose of this double-blind study was to compare the therapeutic effects of a low initial dosage of acitretin, increased at 2-week intervals (group 1:10, 30, 50 mg/day) with a high initial dosage decreased at similar intervals (group 3: 50, 30, 10 mg/day) and with a constant dosage (group 2: 30 mg/day) in 66 patients (47 men and 19 women) with severe psoriasis. At the end of the double-blind phase the mean percent improvement calculated by the Psoriasis Area and Severity Index score, was as follows: 62.7% in group 1, 55.9% in group 2 and 67.1% in group 3.The double-blind phase of 6 weeks was followed by an open phase of 6 weeks, during which the patients were treated either with 10, 30 or 50 mg/day, according to the therapeutic response. At the end of treatment (12 weeks), a mean improvement of more than 80% was obtained in all three groups. Hypervitaminosis A signs and symptoms were observed in all patients. The frequency and severity of these adverse reactions were shown to be dose-dependent. This study shows that a low dose progressively increased is advisable because of similar activity and better acceptability.