Background: Intestinal nutrients induce gut reflexes and modulate perception. Aim: To elucidate the relative potency and putative relationship of motor and sensory effects induced by different nutrients. Methods: By paired tests carried out in sequence on healthy patients, the effect of isocaloric duodenal infusions of carbohydrates and lipids was determined on gastric compliance and on perception of gastric distension. Gastric distension at stepwise tension increments was applied using a tensostat, and perception at each tension level was measured on a 0-6 scale. In separate groups (n = 8 each), three nutrient loads were tested: (A) low (0.2 kcal/min), (B) medium (0.5 kcal/min) and (C) high (1 kcal/min). Results: Values are mean (standard error). (A) Low caloric loads: both gastric perception and compliance were similar with lipids (45 (2) g, 451 (28) ml tolerated) and carbohydrates (46 (1) g, 449 (22) ml tolerated). (B) Medium caloric loads: although perception remained unchanged (46 (1)g and 46 (2) g tolerated, respectively), lipids, but not carbohydrates, partially relaxed the stomach (559 (18) v 442 (31) ml intragastric volume, respectively; p<0.05). (C) High caloric loads: lipids markedly reduced gastric tolerance and increased compliance (22 (3) g, 635 (34) ml tolerated), whereas carbohydrates did not affect perception and induced only a partial gastric relaxation (46 (1) g, 565 (46) ml tolerated; p<0.05 v lipids for both). Conclusion: The effects of intestinal nutrients on gastric tone are more potent than those on gastric sensation, and both depend on the caloric load and the type of nutrient.