The present study examined the effects of the glycemic index (GI) of post-exercise carbohydrate (CHO) intake on endurance capacity and the metabolic responses during exercise the following day. Nine active males participated in two trials in a randomised crossover design. The experimental protocol was completed over two days. On day 1, subjects completed a 90 min treadmill run at 70% VO2 max (R1). Thereafter, they were supplied with a diet consisting of either high glycemic index (HGI) or low glycemic index (LGI) CHO and provided 8g CHOkg body mass (BM)-1.On day 2, after an overnight fast, subjects ran to exhaustion at 70% VO2 max (R2). Eight subjects completed both performance runs (R2). Run time to exhaustion during R2 was longer in the LGI trial (108.9 7.4 min) than in the HGI trial (96.9 4.8 min) (p<0.05). Average RER values were higher in the HGI trial compared to the LGI trial (p<0.05). Fat oxidation rates and free fatty acid concentrations were higher in the LGI trial than the HGI trial (p<0.05). The results of the study suggest that the increased endurance capacity during R2 was largely a consequence of the greater fat oxidation following the consumption of the LGI meals.