This volume places more emphasis on endogenous mediators of gut motility than on drugs used to treat patients with deranged motility. In this respect it resembles most other books on gastroenterology, for while only a relatively small number of drugs are really useful for a rational therapy, a tremendous amount of data is available on neural and hormonal factors regulating the motility of the alimentary canal. Moreover, it must be considered that some of the drugs which can routinely be employed to modify deranged motility of the digestive system are represented by pure or slightly modified endogenous compounds (e. g. , cholecystokinin, its C- terminal octapeptide and caerulein), and it is easy to foresee that their number is destined to increase in the near future. Other drugs are simply antagonists of physiological substances acting on specific receptors (e. g. , histamine H -blockers 2 and opioid compounds). The real explosion of research in this field and the extreme specialization often connected with the use of very sophisticated techniques and methodologies would probably have required a larger number of experts to cover some very specific fields from both an anatomical (lower esophageal sphincter, stomach, pylorus, small and large intestine) and a biochemical (hormones, candidate hormones, locally active substances, neurotransmitters etc. ) point of view.