Sales of caffeinated energy drinks and shots saw double-digit growth in the past few years. Whereas the number of athletes who use energy drinks is unknown, the number of college athletes who report using energy drinks is about 45%. Caffeine in small doses (2–3 mg/kg per body weight) is an effective ergogenic aid, acting on the central nervous system to delay fatigue and increase alertness. Energy drinks claim to have other functional ingredients that enhance athletic performance, but research on energy drinks in athletes is scant and results equivocal. If there is a positive effect, it is the caffeine in energy drinks that provides a performance boost. This article reviews use and safety concerns of energy drinks, the role of caffeine on sports performance, and guidelines for use in athletes.