Doping in sport counts as a typical example of unfair behaviour and a good illustration of ethical problems produced by enhancement activities. However, there are some authors who argue that enhancement in sport is not intrinsically problematic but only so in those circumstances that make it dangerous for athletes or unfair to competitors, or which give rise to suspicion in the viewing public. In contrast to this, the author of the present article shows that enhancement activities are contradictory to basic (...) requirements and preconditions of sports competitions. These preconditions are, firstly, a basic equality of opportunities for all competitors and, secondly, a clear causal connection between a specific performance and an individual athlete, in the sense of authorship of that performance. It cannot be excluded that there could exist future sports competitions without these qualities, but this would clearly be a fundamentally different kind of sport from nowadays. Therefore, the normative background of the current concept of sports competitions, as such, limits the use of enhancement practices to a rather low level. (shrink)