Ulcerative colitis and Crohn's disease remain a great therapeutic challenge to the medical community. In recent years knowledge about the pathogenesis of these diseases has progressed rapidly but the cause of the diseases remains completely unknown. It has become clear that dysregulation of the mucosal immune system is the basis for the chronic evolution of the diseases in a genetically susceptible population. Exciting new therapeutic approaches have been attempted in the last couple of years and cytokine and anti-cytokine treatments in particular seem very promising, especially in intractable disease. The format of the Falk Symposium 106 on Advances in Inflammatory Bowel Diseases', held in Brussels, Belgium, June 18-20, 1998, was somewhat innovative as each session attempted to link the new insights into pathogenetic mechanisms with new therapeutic approaches, resulting in optimal information transfer. The classic therapeutic schemes were updated with a special focus on step-wise build-up of therapy.

Although the first description of patients with what we now call Crohn's disease or ulcerative colitis was published well before 1900, both disorders seem to be diseases of the twentieth century. At the very start of the twenty-first century, it therefore seems appropriate to look back and at the same time look forward and to assess what knowledge has been gained during the last 100 years and in what direction research and thereby clinical practice will go in the future. This book, the proceedings of Falk Symposium No. 111 held in Freiburg, Germany, on June 19-20 1999, contains contributions from experienced senior scientists on the state of the art in pathophysiology, diagnosis and treatment, together with unpublished and new findings from young researchers. Basic scientists and clinicians are thereby involved in an exchange of information which will lead to new directions for future research and clinical management of inflammatory bowel diseases.