Psoriasis is recognized as a T-cell-mediated inflammatory skin disease. Therapies using new biologics that target T cells or inhibit post-secretory cytokines have been developed to treat the immunologic basis of psoriasis. Alefacept and efalizumab inhibit T cell activation by blocking co-stimulatory signals. Etanercept, infliximab, and adalimumab inhibit the activity of TNF-α. Alefacept, efalizumab, and etanercept have been approved by FDA, and infliximab and adalimumab are in the late stages of clinical development in the USA. Clinical trial data have supported the efficacy and safety of these biologic therapies. Broad-spectrum immunosuppressive agents and phototherapy have limitations and toxicities associated with their use. These new biologics have the potential to provide patients with options for safe and effective long-term control of their psoriasis.