Psoriasis is a life-long chronic relapsing dermatosis that shows waxing and waning of disease despite of a lot of conventional treatment. Severe psoriasis, usually defined by a psoriasis area and severity index (PASI) score of more than 10 and an area of involved skin of more than 10%, is a typical indication for biologic therapy. TNF-alpha inhibitors (etanercept, infliximab, and adalimumab) and an IL-12/23 inhibitor (ustekinumab) are the major biologics currently available for psoriasis. After the introduction of biologic treatment, many patients with severe psoriasis experience dramatic improvement of their disease without many side effects and are able to maintain a long-term remission period. Long-term follow up of the side effects of currently available biologics reveals no increase in adverse events compared with non-psoriatic individuals. However, the high cost of psoriasis biologics is a major remaining hurdle for the prescription of these agents to patients with severe psoriasis.