The effects of sham feeding on gastric motility of human subjects have not previously been studied. The amplitude of 3-cpm electrogastrogram (EGG) waves increases after the ingestion of food. We hypothesized that sham feeding would stimulate a similar, but briefer gastric myoelectric response. Healthy human subjects chewed and expectorated a hot dog on a roll and later ate a second hot dog. EGGs were continuously recorded before, during, and after sham feeding and eating. The results of experiment I (N=27) showed that the hand-scored amplitude of the 3-cpm waves increased significantly (P<0.01) during sham feeding. Two minutes after sham feeding, the mean amplitude of 3-cpm EGG waves returned to baseline level. The increase in EGG amplitude during eating was also significant (P<0.01), and remained increased for approximately 30 min after ingestion. The procedure used in experiment II (N=20) was similar to experiment I, but EGGs were computer analyzed and power, ie, spectral intensities, at 3 cpm were obtained. The increase in power at 3 cpm during sham feeding and during eating was significant (P< 0.05 and P<0.02, respectively). Similar to experiment I, the duration of increase in power at 3 cpm was brief during sham feeding compared to the postprandial increase. Four vagotimized subjects failed to show an increase in power at 3 cpm in response to sham feeding. We conclude: (1) The cephalic—vagal stimulation of sham feeding increases briefly the amplitude and power of 3-cpm gastric myoelectric activity in healthy subjects but not vagotomized patients. (2) The increase in postprandial 3-cpm amplitude is prolonged, reflecting initial cephalic-vagal activity and subsequent gastric stimulation by luminal contents.