Psoriasis is a genetically determined inflammatory and proliferative disease of the skin, presenting with sharply demarcated scaly plaques, especially on the extensor prominences and the scalp. Although it is a clinical diagnosis, biopsy can help to confirm the diagnosis. Treatment modalities include topical corticosteroids, tar preparations, vitamin D analogues, systemic retinoids, immunosuppressive drugs, phototherapy, and recently, biologicals.