Inflammatory bowel disease is a chronic inflammatory condition of the gastrointestinal tract that manifests as ulcerative colitis and Crohn disease. Both these clinical entities result from interrelated genetic and environmental factors that may be channeled through an abnormality in mucosal immune function, possibly due to dysregulated or excessive T helper cell (T(H))1 (Crohn disease) or T(H)2 (ulcerative colitis) responses. This article reviews current knowledge of the role of immune factors in inflammatory bowel disease and the potential therapeutic strategies that target the pathways of T(H)1- or T(H)2-induced inflammation.