In western civilization, circadian rhythms of the gastrointestinal tract are dominated by a digestive-interdigestive rhythm: During the day interdigestive activity is rare because of frequent meal intakes prior to termination of preceding fed states: in contrast, nocturnal activity is largely interdigestive. Digestive and interdigestive functions are characterized by specific and interactive motor and secretory activity patterns. When exogenous influences via food intake are prevented, additional, underlying, endogenous, circadian rhythms are observed that modulate gastric and intestinal motility in a characteristic fashion, possibly with tight links to the central nervous system. It is likely that disturbances of physiologic circadian modulation of gastrointestinal function may have pathogenic importance.