In the wake of Knud Enemark Jensen’s drug-related death in 1960, the sporting world expressed shock that an amateur athlete would dope. For many, such an action directly contradicted amateur ideals. Yet historians heretofore have yet to examine the intellectual development of such anti-doping ideology. Following is an intellectual history of the early development of anti-doping, an ideology that emerged bound to the gospel of amateurism. Indeed, amateurism provided the intellectual soil in which anti-doping attitudes germinated. As the search for performance-enhancing substances increased near the end of the nineteenth century, many amateur athletes showed no moral qualms with doping. Over time, however, advocates of amateurism—consisting of various segments of middle-and upper-class society—used anti-doping to reaffirm middle-class values and marginalize the accomplishments of working-class professional athletes. Through amateurism, individuals and sporting communities turned doping from a tacitly tolerated practice to one that contradicted the spirit of sport and constituted a serious threat to sport’s moral integrity.