Psoriasis is now recognized as the most prevalent T-cell-mediated inflammatory disease in humans. While there are a wide variety of therapies that are indicated for the management of psoriasis with different modes of action and different effects, currently, psoriasis is considered as an incurable disease. Biological agents interfere with specific components of the autoimmune response and offer a new therapeutic approach to psoriasis. Efalizumab is a recombinant, humanized immunoglobulin G1 anti-CD11a monoclonal antibody that has been developed for the potential treatment of plaque psoriasis. It has been demonstrated in Phase III clinical trials to have a rapid onset of clinical response and to control chronic moderate-to-severe plaque psoriasis over 1 year of treatment. It has also been reported to have a positive impact on patient quality of life.