Medium-chain triglycerides are known to induce diarrhea, possibly resulting from accelerated intestinal transit. We performed antroduodenal manometry and lactulose hydrogen breath testing simultaneously in eight healthy subjects in order to determine the effects of intraduodenally administered medium-chain triglycerides (MCT) and long-chain triglycerides (LCT) on gastrointestinal motility and small bowel transit time. LCT (15 mmol/hr) induced a fed motor pattern. In contrast, during MCT, in both equimolar (15 mmol/hr; MCT-1) and equicaloric (30 mmol/hr; MCT-2) amounts comparable to LCT, interdigestive motility was preserved but with a significantly (P < 0.05) shorter MMC cycle length (MCT-1, 65 +/- 7 min; MCT-2, 53 +/- 6 min) compared to control (saline infusion; 127 +/- 14 min), Duodenocecal transit time (DCTT) was significantly (P <: 0.05) accelerated during administration of MCT (MCT-1, 56 +/- 6 min; MCT-2, 69 +/- 9 min) and was not affected by LCT (105 +/- 13 min) when compared to control (101 +/- 9 min), In conclusion: MCT, in contrast to LCT, preserve interdigestive motility with a shorter MMC cycle length and accelerate DCTT.