This article examines how professional female tennis players react to (a) prize incentives and (b) heterogeneity in ex ante players' abilities. It is found that a larger prize spread encourages women to increase effort, even when controlling for many tournament and player characteristics. Further results indicate that uneven contests lead favorites to win more games and underdogs to be less performing. They also show that the performance differential among players increases with the ranking differential. These findings suggest that the outcome of a match is more linked to players' abilities than to players' incentives to adjust effort according to success chances.In traditional business activities, many organizations use payment schemes based on relative or rank performance to foster the average worker's effort. One may argue that, in the sports industry, the organizers of competitions must also set up a structure of prizes that maximizes the performance of players (Szymanski, 2003). Indeed, if players put forth more effort, the competition is more attractive. The crowd, the media, and the sponsors are more interested in the competition, which in turn increases the income of the organizer. In other words, as managers of firms AUTHORS' NOTE: The authors would like to thank two anonymous referees for many useful comments and suggestions on an earlier version of this article. We are also most grateful to Tor Eriksson, Maria Jepsen, and Benoît Mahy for helpful advice. Any remaining errors are those of the authors.