Caffeine is the most commonly used drug in the world, often consumed in the form of coffee, sodas, teas, energy drinks, and chocolate. It is also generally regarded as very safe to consume. As one of the most thoroughly investigated sport supplements, it has been well established as an ergogenic aid for endurance performance, and has been shown to increase time to exhaustion, increase mean power output during time trials, and decrease perceived exertion. The effects of caffeine on measures of muscular endurance and repeated anaerobic performance are currently much more equivocal, and elicit further investigation. The first purpose of this study was to determine the effects of Red Bull Energy Drink (2.0mg CAF/kg BW) on anaerobic power using repeated Wingate cycle performance compared to a placebo. Additionally, this study sought to determine the effects of Red Bull Energy Drink on elbow flexor muscle endurance compared to a placebo. The study used a double-blind, repeated-measures, crossover, counter-balanced design. The eighteen male subjects that participated in this study were between 18 and 35 years old, with a mean age of 23.4 years. They had a mean weight of 81.3 ± 10.2 kg, mean height of 1.81 ± 0.08 m, and mean BMI of 24.76 ± 2.89 kg/m2. Three to seven days after the familiarization trial, subjects will be randomly assigned to supplement with Red Bull (2.0 mg/kg caffeine) or an isovolumetric amount of placebo (non-caffeinated Mountain Dew) 60 minutes before performing the exercise tests. The Subjects performed three sets of maximal isokinetic elbow flexion for 60 seconds at 0.52 rad/s (separated by two minute rest intervals) on the Biodex System 3 Isokinetic Dynamometer. Following the isokinetic testing, subjects performed three 30-s Wingate anaerobic cycle tests (separated by two minute rest intervals) at a load corresponding to 0.075 kpal/kg body mass (Bar-Or, 1987). There was no significant difference found for Peak Torque or Decline in Peak Torque for elbow flexor muscle endurance compared to placebo. No significant difference was found in Peak Power and Mean Power for the Wingate Anaerobic Test. There was a significantly (p<0.05) greater decline in Mean Power and Relative Mean Power for Red Bull compared to placebo, inferring that there may be a detrimental effect on repeated anaerobic performance following ingestion. Decline in mean power from the first to the third set of Wingate testing was 182.15 +/- 59.97 W for Red Bull trials, and 153.87 +/- 67.08 W for placebo trials. The relative decline in mean power relative to each subject's body weight for Wingate testing was 2.25 +/- 0.751 W/kg for Red Bull trials, and 1.88 +/- 0.777 W/kg for placebo trials. While there is unlikely one single mechanism explaining the findings from this study, results may be partially explained by increased concentrations of lactate in either the blood or muscle, or lowered concentrations of plasma potassium following caffeine ingestion compared to placebo.