We study strategic choice of effort in best-of-three contests between equally skilled players. Economic theory predicts such contests are more likely to end in two rounds than in three. If, however, a contest reaches a third round, each player is equally likely to win. We test these predictions with data from professional tennis matches, using betting odds to identify equally skilled opponents. The empirical results support the theoretical predictions, suggesting players strategically adjust efforts during a best-of-three contest.