Self-monitoring of plasma triglycerides (TG) may be a very useful tool to monitor, on a daily basis, the TG responses to different nutrients, particularly carbohydrates (CHO) and fat, whose influence on postprandial TG levels is not very well known. Therefore, the aim of the present study was to evaluate the TG response of hypertriglyceridemic patients to a similar amount of calories deriving from different sources of CHO and fat. Thirty-nine hypertriglyceridemic patients were randomly assigned to 1 of 2 experimental groups. In 1 group (the fat group), patients were given a standard meal plus a fat supplement of 300 kcal derived from different types of fat (butter, sunflower margarine, olive oil) for dinner, once a week for 3 weeks. In the other group (the CHO group), patients consumed the same standard meal plus a supplement of 300 kcal derived from different types of CHO (bread, coke, fruit). In both groups, patients measured their plasma TG before and 3 hours after each meal by Accutrend GCT (ROCHE, Mannheim, Germany). A subgroup of patients (n = 18) also performed TG determinations 2 hours after the test meals. The 3-hour TG increments were not significantly different between the different test meals (f = 0.671; P =.52); instead, the TG increments induced by fat supplements were significantly higher than those induced by the CHO supplements (f = 14.31; P =.0001). Similar results were also obtained 2 hours after the test meals. In conclusion, this study shows that the 2- and 3-hour TG responses to fat are higher compared with that induced by carbohydrate. This point, especially if confirmed by experiments with more frequent after meal measurements and of longer duration, should be taken into account in defining the best dietary approach to lower plasma TG levels throughout the whole day.