The histologic and immunologic findings on psoriasis have led to the development of biologic therapies for its treatment. Biologic therapies are classified according to their structure as recombinant human proteins, monoclonal antibodies, and fusion proteins. Currently there are five biological drugs approved by the Food and Drug Administration for the treatment of psoriasis; however research studies are being performed to implement a few others. It is important to be familiarized with biological drugs, understand their mechanisms of action, and their adverse effects in order to be able to provide patients the most adequate therapeutical alternative. Advances in biotechnology provide new strategies that act on the immune system. The clinical experience using biological therapies in dermatology is relatively limited and there is a need to define which patients are candidates to receive these drugs. The combination of biologic treatments with traditional drugs needs further research since this could enhance their benefits, limit their toxicity, and reduce costs.