This study was undertaken to determine the effect of medium-chain triglyceride (MCT) oil supplementation on the duration and episodes of diarrhea attacks, and specifically its effect on the clinical manifestations of patients. Seventeen children aged 6 months to 47 months old with a mean age of 19.6 months, suffering from acute diarrhea at the Pediatric Ward of the Philippine General Hospital Medical Center and other neighboring health centers were studied. A double-blind randomized design was employed. Physical and clinical assessment was performed by a physician prior to enrolment in the study. Dietary, anthropometric, and biochemical assessment were undertaken by clinical investigators before and after the supplementation. The subjects were randomly assigned to either the MCT oil- supplemented diet or the non-MCT oil diet. Daily monitoring of food intake and the frequency or episodes of diarrhea attacks was done. Subjects were closely monitored for any possible adverse reactions. The baseline characteristics of the subjects were not significantly different for any of age, height, weight, cholesterol or triglyceride concentrations between the two groups. Nutrient intakes at baseline and during intervention were also not significantly different. There were no differences in cholesterol and triglyceride between the two groups after supplementation. Stool frequencies of the MCT group and the non-MCT group at baseline, after the 6th hr, and at 12th hour, were not different. No subject developed fat malabsorption during the intervention, as assessed with Sudan Black stain. There was statistical significant difference in the rate of weight gain among subjects in the MCT group compared to subjects in the non-MCT group , but a trend in this direction (0.22 + 0.22 kg/day vs -.048 + .26 kg/day), (p=.042). MCT oil may promote weight gain (although what this constitutes in body compositional terms is uncertain) and shows a trend towards shorter duration of intervention among children with acute diarrhea. Limited sample size precludes conclusions on these possibilities. MCT oil did not cause vomiting, dehydration, or fat intolerance. MCT oil did not cause an elevation in cholesterol and triglyceride levels. More studies, with larger sample size, and longer duration will be worthwhile to assess the effect of MCT oil on childhood diarrhea.