The glycemic index (GI) represents the relative postprandial blood glucose response to the ingestion of a food containing carbohydrate. Although regular physical exercise may influence glucose metabolism, it is not yet known if chronically performed exercise also affects the GI. The objective of this study was, therefore, to determine the GI of common meals (three breakfast cereals: B, C, D) in healthy, nonsmoking young males who were either endurance-trained (n = 12) or sedentary (n = 11). Glucose was used as the reference food. The GI value between the endurance-trained and sedentary subjects differed significantly (p < 0.01). Pair-wise comparisons between endurance-trained and sedentary subjects within the different test meals were significant for test meal D (p = 0.002), marginally non-significant for meal C (p = 0.052) and not significant for meal B (p = 0.204). These results suggest that the GI of some complex foods may depend on the training status of healthy young subjects.