Ulcerative colitis and Crohn's disease, the idiopathic inflammatory bowel diseases (IBD), are thought to represent genetically determined, dysregulated immune responses to otherwise innocuous luminal antigens. Although progress in research has advanced our understanding of the immunopathogenesis and begun to elucidate genetic contributions toward susceptibility, limitations of current medical approaches continue to drive the search for better therapeutic agents. Most recently, the introduction of infliximab has heralded a new era of evolving biologically targeted treatments for IBD. Infliximab is currently the only biologic agent approved for the treatment of inflammatory and fistulizing Crohn's disease, but ongoing research continues to generate new biologic agents targeted at specific pathogenic mechanisms involved in the inflammatory process. Undoubtedly, with the success of infliximab, the role of biologic therapy will continue to expand in the future treatment of IBD.