Basal fluctuations of motilin and their correlation to intestinal motor activity were studied in five hypophysectomized (anterior lobe resection) patients. A cyclic pattern of motor activity identical to the one described in normal volunteers was observed. The mean interval between two activity fronts (AF) was 115 min, which is not significantly different from the normal length. Motilin levels were within the normal range, and fluctuations correlated with the occurrence of an AF. The mean difference between motilin levels 15 min before the AF and at the time of the start of the AF was +15 pM (P less than 0.05). For the levels 15 min after the AF the mean difference was -9 pM (P less than 0.05). These values correlate well with those reported by us in normal volunteers, in whom the mean differences were +11 pM and -14 pM, respectively. It is concluded that the adenohypophysis is not involved in the regulation of motilin levels or in the regulation of interdigestive motility in man.