Despite intense investigation, the etiology of inflammatory bowel disease (IBD) remains unknown. Recent studies with new therapeutic agents provide insight into the pathogenesis of IBD through analysis of the clinical response to pharmacologic agents whose mechanism of action is understood. Until new agents are established, IBD will be treated with conventional drugs directed toward modifying the inflammatory responses responsible for gastrointestinal mucosal damage. Sulfasalazine, mesalamine (5-aminosalicylic acid), and corticosteroids will continue to be the mainstay of therapy for the foreseeable future. Antibiotics such as metronidazole and immunosuppressants such as 6-mercaptopurine and methotrexate are useful in Crohn's disease and ulcerative colitis in selected cases. Many new exciting agents are being investigated and show encouraging results in the treatment of IBD. This article reviews the agents used in IBD with an emphasis on new therapeutic agents.