The meeting that provided the material for this book was the 58th Symposium of the Federation of European Microbiological Societies (FEMS) entitled MOLECULAR PATHOGENESIS OF GASTROINTESTINAL INFECTIONS which was held in Helsingor, Denmark from 2nd to 4th September, 1990. The aim of this meeting was to bring together scientists from a range of discipline- microbiology, cell biology, molecular biology and immunology - to consider how microbes, including parasites, colonize and infect the gastrointestinal tract. The programme was designed to focus particular attention on the range of strategies whereby enterovirulent bacteria and parasites colonize the gastrointestinal mucin layer, how they adhere to and penetrate the epithelial layer by entering the cells or passing between them, and how various protein toxins may facilitate these processes. Speakers were especially encouraged to highlight the recent expansion in our knowledge of the molecular mechanisms by which enterotoxigenic and enteropathogenic Escherichia coli, shigellae, salmonellae and Yersinia enterocolitica cause intestinal disease. There were also discussions of recently-discovered gastrointestinal pathogens such as Clostridium difficile and Helicobacter pylori as well as accounts of how virulent determinants can be used to develop new diagnostic methods based on DNA gene probes and the polymerase chain reaction (PCR). These presentations provided the basis for the chapters in this book.