Thirteen patients with severe persistent psoriasis, intolerant of, or unresponsive to, other current treatments have been treated with cyclosporin (Cys) for periods varying from 12-25 (mean 18) months. The dose ranged from 1-4 mg/kg/day (mean 2.8 mg). There was a 72% reduction in the mean PASI score at 4 weeks, and at the end of the study, an 81% reduction. Adjuvant therapy with topical steroids was used in 11 of the 13 patients after the first 3 months of Cys treatment to persistent patches on an intermittent basis with beneficial effect. Six patients developed mild to moderate hypertension, in three this was controlled by a reduction in the dose of Cys, and in the other three by hypotensive agents. The mean serum creatinine rose from 72 to 90 microM/l during the study. Hypertrichosis occurred in seven of the 13 patients. Low dosage Cys is an effective treatment for clearing psoriasis and maintaining improvement on a long-term basis.