Intraduodenal lipid infusion induces symptoms and increases sensitivity to gastric distension in patients with functional dyspepsia. To test whether these effects are specific for lipid, we compared the effects of intraduodenal infusions of either lipid or glucose on symptoms and gastric sensory and motor responses to gastric distension. Eighteen dyspeptic patients and nine controls were studied. The stomach was distended with a flaccid bag during isocaloric infusions (1 kcal/ml) of saline and either 10% Intralipid (nine patients) or 26.7% glucose (nine patients) into the duodenum. Dyspeptic symptoms and sensory thresholds for epigastric fullness and discomfort were assessed. Gastric pressure profiles during distensions were similar during lipid and glucose infusions in patients and controls, but both were significantly lower than during saline infusion. Lower volumes were required to induce fullness and discomfort in the patients compared with the controls. In the controls, the threshold volumes required to induce fullness and discomfort were greater during infusion of lipid and glucose than during saline infusion, but in the patients, the threshold volumes were increased during glucose infusion but further reduced during lipid infusion. Moreover, in the patients, nausea was more common during lipid than glucose infusion and did not occur during saline. The controls did not experience any symptoms during any infusion. In conclusion, intraduodenal lipid but not glucose sensitizes the stomach to distension in patients with functional dyspepsia but not in controls.