Acute changes in the blood glucose concentration affect the intensity of gastrointestinal sensations. The aim of this study was to examine the effects of hyperglycemia on cortical potentials evoked by esophageal distension. In 16 healthy volunteers, a balloon was positioned in the lower esophagus. A series of 50 distensions was performed at both a lower volume (producing definite sensation) and a higher volume (producing unpleasant sensation), at blood glucose concentrations of 5 and 13 mmol/liter. Triphasic cortical potentials were recorded from a midline scalp electrode (Cz). During euglycemia, interpeak amplitudes were greater at the higher than the lower balloon volume (P < 0.005). At the lower balloon volume, the interpeak amplitudes were greater during hyperglycemia than euglycemia (P < 0.05). There was no effect of the blood glucose concentration on amplitude at the higher balloon volume. We conclude that in healthy subjects, the amplitude of the cortical response to moderate, but not unpleasant, esophageal distension is greater during hyperglycemia when compared to euglycemia. These observations are consistent with the concept of increased intensity of gut sensation during hyperglycemia.