Background: Ginseng has been used as an ergogenic agent, although evidence for its effectiveness is weak. A randomized, double-blind, placebo-controlled clinical trial was conducted to evaluate the effect of a ginsenoside complex (UG0712) on changes in exercise performance. Methods: Sedentary individuals (n=117) were randomly assigned into one of three groups: low-dose ginsenoside supplementation (100 mg/d, n=39), high-dose ginsenoside supplementation (500 mg/d, n=39), or a placebo group (500 mg/d, n=39). All participants underwent a supervised 12-wk aerobic and resistance exercise training course. To assess the effects of supplementation on physical performance, maximal oxygen consumption (VO2max), anaerobic threshold (AT), lactic acid, and muscle strength of the dominant knee were measured at baseline, every visit, and after the training program. Results: Both ginsenoside groups showed significant increases in VO2max and muscular strength during exercise training. There were no definite changes in AT and lactic acid levels over time. After exercise training, there were definite differences in the VO2max (28.64.9 to 33.7±4.9 ml/kg/min in high-dose group vs. 30.4±6.7 to 32.8±6.6 ml/kg/min in placebo, p=0.029) and AT (19.3±4.2 to 20.9±3.5 ml/kg/min in high-dose group vs. 20.0±5.1 to 20.0±4.9 ml/kg/min in placebo, p=0.038) between the high-dose ginsenoside and placebo groups. However, there was no difference in VO2max between the low-dose ginsenoside and placebo groups (p=0.254). There were no differences in muscular strength during exercise training among the three groups. Conclusion: High-dose ginsenoside supplementation (UG0712) augmented the improvement of aerobic capacity by exercise training. Keywords: cardiopulmonary exercise test, ginsenoside, Panax ginseng, randomized controlled trial