1. The influence of gastrointestinal infusions of fat on short-term and 24 h control of food intake were studied in twenty-four pigs fed twice per day and seventeen fed three times per day. The pigs were fitted with up to four catheters placed in the stomach, the duodenum, and at 2, 4 and 8 m from the ligament of Treitz. 2. Various infusions were given into the catheters beginning 30 min before the first meal (two feeds) or second meal (three feeds) of the day and continuing until the end of the feeding period or until the pigs stopped eating. 3. Infusions of a fat emulsion (Intralipid) into the stomach, of oleic acid or glycerol into the duodenum, or of glycerol into the ileum (8 m from the ligament of Treitz) inhibited food intake during the infusion according to the amount of energy infused. 4. Food intake was inhibited by more than the amount of energy infused with duodenal infusion of Intralipid or monoglyceride, or with infusion of Intralipid mixed with bile salts and lipase (but not with Intralipid alone) into 2 or 4 m from the ligament of Treitz. 5. Duodenal infusion of glycerol, and ileal (8 m from the ligament of Treitz) infusion of monoglyceride or glycerol inhibited food intake at the following meal according to the amount of energy infused. 6. It is concluded that fats can exert both pre- and post-absorptive control of food intake and that since Intralipid infusion to the stomach but not to the duodenum inhibits food intake according to the amount of energy infused, it is likely that control of food intake is related to control of stomach emptying. 7. The inhibition of food intake by more than the amount of energy infused during upper intestinal infusion of fat is likely to be a result of digestion of the fat to monoglycerides, and interaction of monoglycerides with receptors in the proximal 4 m of intestine.