The gastrointestinal tract has a number of unique features. Its extensive surface is formed by a single layer of rapidly renewing cells, the intestinal epithelial cells. These cells are in contact with a number of other cell populations, including the largest part of the immune system, and with an excessive luminal antigen load, including vast numbers of bacteria. Furthermore two more organs, namely liver and pancreas, are part of the system. The rapid renewal of the epithelial layer, the interactions of different cell types, and the balance between cell proliferation and death, have been fascinating subjects of studies in recent years. Much has been learned, and cytokines have emerged as important mediators for all these interactions and homeostatic systems. This book, the proceedings of the Falk Symposium 113 on `Cytokines and Cell Homeostasis in the Gastrointestinal Tract', held in Regensburg, Germany, 16-18 September 1999, provides a forum for basic scientists and interested clinicians to exchange ideas, to discuss concepts and to plan further studies.

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from experienced senior scientists on the state of the art in pathophysiology, diagnosis and treatment, together with unpublished and new findings from young researchers.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.