The following paper is a review of the benefits of natural and artificial ultraviolet light in psoriasis. Phototherapy has been administered alone or in combination with topical corticosteroids, tars, anthralin, calcipotriene, and tazarotene, and with systemic therapies, such as methotrexate, acitretin, and cyclosporine. The choice of treatment with ultraviolet light B or psoralen plus ultraviolet light A is based on a history of previous response to treatment, skin type, severity of psoriasis, and patient considerations, including compliance and responsibility for observing the precautions to avoid potential side effects.