Since the dawn of athletic competition during the original Olympic Games in Ancient Greece, athletes, as well as their coaches and trainers, have been finding innovative ways to gain an edge on their competition. Some of those performance-enhancement methods have been within the accepted rules while other methods skirt the gray area between being within the rules and not, while still other methods break the established rules. In modern times, doping - the use of performance-enhancing drugs - has been one method athletes and their trainers have used to beat their competition. The history of sports doping during the modern era can be traced through the events and scandals of the times in which the athletes lived. From the use of amphetamines and other stimulants in the early 20th century, to the use of testosterone and steroids by both the USSR and the United States during Cold War-era Olympics games, to blood doping and EPO, to designer drugs, the history of doping in sports closely follows the medical and technological advances of our times. In the early 21st century, the possibility of genetically engineered athletes looms. The story of doping in sports over the last century offers clues to where the battle over performance enhancement will be fought in the years to come.