The purpose of this study was to investigate the acute effect of capsaicin supplementation on performance, rate of perceived exertion and blood lactate concentrations during resistance exercise in healthy trained young men. Ten resistance-trained men (age= 22.7±4.0 yrs, weight= 82.3±9.6 kg, height= 1.75±0.1 cm) completed two randomized, double-blind trials: Capsaicin condition (12mg) or a placebo condition. Forty five minutes after supplement consumption, subjects performed four sets until movement failure in the squat exercise at 70% of 1RM with 90 seconds of rest interval between sets. The total weight lifted (total repetitions x weight lifted) was calculated. The rate of perceived exertion (RPE) was recorded after the last set. Blood lactate was analyzed after each set of exercise, immediately post exercise, and after three, five and at 30 minutes during recovery. The number of repetitions in each set decreased significantly after all sets compared to set-1 and after set-3 and set-4 in relation to set-2 (p<0.001), however total weight lifted was higher in capsaicin compared to placebo (3919.4 + 1227.4 kg vs 3179.6 + 942.4 kg, p=0.002). Blood lactate increased significantly following each set (p<0.001); however, there were no differences between conditions. RPE was significantly less for the capsaicin condition than placebo (17.2 + 1.0 vs 18.3 + 1.7, p=0.048). In summary, acute capsaicin supplementation improves lower body resistance training performance in trained young men.