The aim of this symposium was to provide a framework for fruitful discussion on intestinal transport, not only for advanced scientists but also for younger people starting in this field of research. Invited lectures, communications and poster presentations were focused on four central themes, all treating the prop erties of the sole intestinal epithelium, deliberately leaving aside problems dealing with more integrative functions of the whole intestine. The importance of motility or blood circulation, for instance, is certainly capital in the overall intestinal function, but these aspects by themselves deserve another meeting. This volume has compiled the manuscripts of the invited lectures which sub stantially comprised the four sessions of the Symposium. Part 1 is designed to emphasize actual knowledge of the transport of water, inorganic as well as organic ions and molecules across the isolated intestinal epithelium. An enormous wave of investigations has emerged from studies per formed with "Ussing chambers", which roused interest in studies on absorption mechanisms and subsequently on secretory processes. This has triggered off a trend to research on isolated cells as absorption and secretion are the main func tion of the different cell types constituting the intestinal epithelium. In this first session not only the importance of the parallel arrangement of these different cellular entities is stressed, but also the role played by the paracellular route.