['Fifty patients with severe recalcitrant plaque-type psoriasis were randomized to receive treatment with either oral tacrolimus (FK 506) (n=27) or placebo (n=23) for 9 weeks. The two treatment groups were comparable with respect to baseline demographic data. The initial dose was 0.05 mg/kg per day and, in cases of insufficient efficacy, could be increased to 0.10 and 0.15 mg/kg per day at the end of weeks 3 and 6, respectively. Treatment efficacy was based on the percentage reduction in the Psoriasis Area and Severity Index compared with baseline data. Patients were defined as responding to therapy if the percentage change in the Psoriasis Area and Severity Index from baseline after 3, 6, and 9 weeks was 20% or greater, 45% or greater, and 70% or greater, respectively. Safety was assessed on the basis of all adverse events reported.', 'At the end of week 9, tacrolimus+-treated patients had a significantly greater reduction in the Psoriasis Area and Severity Index than did placebo-treated patients (tacrolimus, -83; placebo, -47; P<.02). Similar numbers of patients in both groups responded to therapy at the end of week 3, but at the end of weeks 6 and 9, more tacrolimus-treated patients responded to therapy (week 6 ,12 tacrolimus- and six placebo-treated patients; week 9, 12 tacrolimus- and three placebo-treated patients). Diarrhea, paresthesia, and insomnia were the most frequently reported causally related adverse events in the tacrolimus-treated group. All of the reported adverse events were mild or moderate in severity, and all resolved without a change in study medication.'] Is systemic tacrolimus ( FK 506 ) effective for the treatment of psoriasis in a double-blind , placebo-controlled study . The European FK 506 Multicentre Psoriasis Study Group?