Various biologic agents have been evaluated in patients with inflammatory bowel disease (eg, Crohn's disease [CD]) and ulcerative colitis (UC). At present, only one, infliximab (humanized monoclonal anti-tumor necrosis factor-α antibody), is approved by the US Food and Drug Administration for induction and maintenance treatment in patients with active moderate to severe and/or fistulizing CD who are refractory to conventional therapy. Two recent trials, Active Ulcerative Colitis Trial (ACT) 1 and ACT 2, observed high efficacy of infliximab in inducting and maintaining clinical remission, mucosal healing, and corticosteroid-sparing effects in patients with moderate to severe UC. A plethora of randomized, double-blind, controlled and open-label, uncontrolled studies on large and small numbers of patients has assessed efficacy and safety of various biologic agents of potential use in treatment of inflammatory bowel disease. With respect to safety of biologic agents used for treatment, the most accurate data are available only in the case of infliximab. This is due to the fact that infliximab was evaluated in many more trials than any other biologic agent. Moreover, postmarketing experience also provides very valuable information about any side effects occurring during treatment with this agent. Copyright © 2006 by Current Science Inc.