The results of recent studies on prediction markets are encouraging. Prior experience demonstrates that markets with different incentive schemes predicted uncertain future events at a remarkable accuracy. In this paper, we study the impact of different monetary incentives on the prediction accuracy in a field experiment. In order to do so, we compare three groups of users, corresponding to three treatments with different incentive schemes, in a prediction market for the FIFA World Cup 2006. Somewhat surprisingly, our results show that performancecompatible payment does not necessarily increase the prediction accuracy.