Human studies using oral cyclosporin A (CyA; Sandimmun) therapy for psoriasis have been in progress for nearly 9 years. Cumulative data of the clinical effects of this therapy in 1000 patients have been collected, and are derived from multiple open and controlled studies. The efficacy of this treatment in psoriasis is well recognized, and the relative safety of up to 2 years of therapy is also established, provided that the guidelines are observed. However, there is concern regarding the long-term safety of CyA treatment of psoriasis as experience is still limited. Careful monitoring of all CyA-treated patients is therefore mandatory, and CyA should only be used by dermatologists who have expertise in its use. During treatment, co-operation with an experienced nephrologist is strongly recommended.