The treatment of ulcerative colitis and Crohn's disease shares certain common principles. Initial treatment is primarily medical for both diseases. The most important drug classes in inflammatory bowel disease are antiinflammatory agents, corticosteroids, and 5-aminosalicylic acid formulations (5-ASA). Corticosteroids and 5-ASA preparations are effective medical treatments in up to 80% of the patients with inflammatory bowel disease. The use of immunosuppressive therapy with drugs such as azathioprine is less established and should be restricted to patients who fail on standard medical treatment.