The purpose of this study was determine effects of ingestion carbohydrate-electrolyte beverage drink to improve exercise performance in the heat. Ten male subjects (age 18-30 years) were subjected to cycle ergometer at 63.5 ± 3.3% of maximal O2 consumption (VO2max) with a pedal speed of 60 rpm until they became fatigued. They were given a drink of carbohydrate-electrolyte at a concentration of 6%, 12% and a flavored water placebo (WP) to consume at a volume of 3 ml/kg/body weight every 20 minutes. Blood samples were taken at rest and during exercise at every 10 minutes for analyzing plasma glucose, insulin, free fatty acid and glycerol. Mean exercise time until the on set of fatigue in subjects was found to be significantly longer (P<0.001) following the ingestion of carbohydrate-electrolyte beverage (84.7 ± 6.9 min) compared with WP (66.2± 2.2 min). However, plasma glucose concentration was found to be significantly lower in the WP ingested subjects compared to carbohydrate electrolyte ingested ones (4.5 ± 0.2 m.mol/L vs 4.3 ± 0.2 m.mol/L, ANOVA, P<0.05). When carbohydrate electrolyte beverage maintained plasma glucose concentration at 4.5 – 5.5 m.mol/L, the subjects exercised for an additional hour before being fatigued. The levels of plasma insulin from 40 minute until the end of exercise were decreased in all beverage ingested subjects. Results indicate that carbohydrate-electrolyte beverage supplementation during prolonged cycling improves physical performance.