The autonomic nervous control of the gastrointestinal canal in vertebrates is reviewed, with special emphasis on the control of gut motility in non-mammalian vertebrates. The presence and function of different established and putative neurotransmitters is discussed. In addition to the presence of adrenergic and cholinergic nerves in the gut, 5-hydroxytryptamine, ATP or a related substance, and several neuropeptides are suggested to act as neurotransmitters in the gastrointestinal canal of vertebrates. Among the neuropeptides demonstrated in the gut of non-mammalian vertebrates by immunohistochemical methods are peptides similar to bombesin, gastrin/cholecystokinin, neuropeptide Y, neurotensin, opioids, somatostatin, substance P (tachykinins) and vasoactive intestinal polypeptide. Functional studies show that many of the substances discussed may well be involved in the nervous control of the gut motility, although the function and mechanism of action varies to some extent between species and between vertebrate groups.