To investigate the effects of fat and carbohydrate on appetite, food intake and gastric emptying with and without the influence of orosensory factors, a group of nine healthy, fasted male subjects took part in two separate paired experiments involving high-fat and high-carbohydrate radiolabelled soup preloads. In the first experiment subjects received direct intragastric isocaloric infusions of either a high-fat tomato soup or a high-carbohydrate tomato soup (400 kcal in 425 mL) over 15 min, on two occasions. In the second paired experiment subjects ingested the same high-fat and high-carbohydrate soup over 15 min. In both experiments ratings of hunger and fullness were recorded over a period of 135 min and gastric emptying was measured by scintigraphy. Food intake was evaluated from a test meal (yoghurt drink) given 2 h after the end of the soup infusion/ingestion. When soup was administered intragastrically (Experiment 1) both the high-fat and high-carbohydrate soup preloads suppressed appetite ratings from baseline, but there were no differences in ratings of hunger and fullness, food intake from the test meal, or rate of gastric emptying between the two soup preloads. When the same soups were ingested (Experiment 2), the high-fat soup suppressed hunger, induced fullness, and slowed gastric emptying more than the high-carbohydrate soup and also tended to be more effective at reducing energy intake from the test meal. The results of these studies demonstrate that orosensory stimulation plays an important role in appetite regulation, and also indicate that subtle differences in orosensory stimulation produced by particular nutrients may profoundly influence appetite and gastrointestinal responses.