The effect of dietary medium chain triglyceride (MCT) on short-term food intake was compared with the effect of long chain triglyceride (LCT) in rats. Corn oil and glyceryl tricaprylate were used as LCT and MCT sources, respectively. Rats were given diets containing 200 g MCT/kg diet (MCT diet), 100 g MCT + 100 g LCT/kg diet (ML diet), or 200 g LCT/kg diet (LCT diet) in Experiment 1. Cumulative food intake was determined every h for the first 12 h, then at 2-h intervals thereafter during the subsequent 12 h. As early as 1 h after feeding, cumulative food intake significantly decreased in MCT-fed animals in a dose-dependent fashion. In Experiment 2, rats were given a choice between MCT and LCT diets for 1 h to confirm whether or not the palatability of diets was influenced by dietary fat sources. There was no difference in food intake between the two diets. In Experiment 3, the responsibility of endogenous cholecystokinin (CCK) for the difference in food intake between the two diets was investigated for 6 h by using a CCK-A receptor antagonist, Devazepide (DVZ, 1 mg/kg b. wt.). Food intake in the MCT diet and also in the LCT diet was improved by DVZ. It is concluded that the satiety, but not the palatability, is affected by carbon chain length in dietary triglyceride sources, although the responsibility of endogenous CCK is very small.