Crohn's disease is a chronic inflammatory condition that may affect any part of the gastrointestinal system and multiple extraintestinal organs. Although its exact pathogenesis remains unknown, increasing evidence suggests an abnormality in the control of "physiologic" inflammation caused by bacterial and other antigens. Diagnosis starts with a careful history and physical examination, and confirmation rests with radiologic and histologic studies. Newer treatments are more specifically targeting the cascade of cytokine-mediated events that perpetuate inflammation.