Although a large therapeutic arsenal of conventional drugs is available to treat patients with psoriasis, a group of patients still exists that fulfill the inherent exclusion criteria or present with subjective or objective side-effects. This necessitates the need for controlled studies with potential new antipsoriatic drugs like cyclosporin A. In this thesis patientoriented studies on the treatment of severe psoriasis vulgaris with systemic low-dose and topical cyclosporin A are presented in an attempt to answer the following questions. A - What is the efficacy of short-term low-dose cyclosporin A in patients with severe, recalcitrant psoriasis ? (Chapters 3 and 4) B - Is there a preferential dose regimen for long-term treatment, either continous or intermittent ? Can the combination with a conventional drug like etretinate produce an additive positive effect ? (Chapter 5) C- Can topically applied cyclosporin A be effective in dermatologic disorders such as psoriasis ? (Chapter 6) D - What are the side-effects of orally administered cyclosporin A ? How can nephrotoxocity be monitored ? What are the recommended guidelines for the practicing dermatologist for using cyclosporin A ? (Chapters 7 and 8)