Few human illnesses today are so challenging, medically, scientifically, and socio-economically, as the "nonspecific" inflammatory bowel diseases (IBD): ulcerative colitis and Crohn's disease. Originating several centuries ago but essentially diseases of the 20th century, often attacking children and young adults, involving all bodily systems as well as the gastrointestinal tract, ulcerative colitis and Crohn's disease have emerged in recent decades as among the more "glamorous" unsolved diseases, presenting unusual opportunities for insightful clinical and investigative study. Many of the prevailing concepts originated during the early and mid 20th century. The purpose of Origins and Directions of Inflammatory Bowel Disease is to review these earlier studies and their evolution "from the mystical to the molecular," and guide investigators and physicians through the challenging clinical and scientific maze of IBD.