In this work, we look into the problem of justifying the ban on doping in sport, identifying doping as the improvement of a sportpersons’ sport results based upon risky and illegal methods. I make a distinction between external and internal accounts that justify the ban on doping. The external accounts justify the ban by claiming that it satisfies some desirable value that are external to sport or participation in sport. Internal accounts, on the other hand, justify the ban by claiming that it realizes values that are internal to sport or participation in sport. It is claimed that the traditional external accounts of justifying the ban in which it is claimed that doping leads to different form of harm, are not satisfactory since we cannot establish a significant ethical difference between harm caused by doping, and harm caused by participation in a sport. Contrary to these accounts, it is claimed that justifying the ban on doping in sport should be based upon reasons internal to sport. According to this account, (i) sport is best understood as a practice, that is, a socially autonomous activity, with specific rules, standards and moral virtues, (ii) athletic using doping is a misunderstanding of the sportperson concerning what it means to be participation aims at acquisition, and development of sport-specific skills, abilities and virtues, and that participating in the sport practice, (iv) that doping is morally dubious since sportpersons’ have utilitarian reasons to acquire the general virtue truthfulness and act in accordance with a self-understanding of themselves as being representatives of the sport practice they are participants in.