There are many separate groups working in gut biology, and they feel that the gut is an excellent model for investigating general problems in differentiation, growth control, stem cell biology, and regeneration and adaptive responses. Part III of the Gastroenterology Symposia Freiburg 1996 (Falk Symposium No. 94), held in Freiburg, Germany, October 25-26, brought together some of these groups with a view to identifying areas which are not being utilized and need to be exploited, such as transgenic and knockout approaches, retrovirus delivery systems, and model cell/tissue systems. The main themes of this text are gastrointestinal development and differentiation, gut stem cell biology, and the control of gut growth in normal and abnormal situations. Basic research findings are related to clinical situations, and the book should appeal not only to gut cell and molecular biologists, but also to gastroenterologists interested in the potential applications of these subject areas.