There is no previous research in tennis doubles tactics and efficiency of tactics. There are several tactical variants for the serving team in tennis doubles; however the classical formation is mostly used. Other tactical variants are Australian formation and I-formation. Our aim was to find, how often and how effectively are these tactical variants used in men’s and women’s tennis doubles at the international level. We observed 22 men’s matches and 24 women’s matches on the ITF tournaments (International tennis federation). Every point that was played was marked. The observers wrote down the used tactical variant of each point and its efficiency. The classical formation dominates in men’s and women’s doubles. Men sometimes used the I-formation. Women used very rarely the Australian formation. In men’s doubles, the I-formation was used more when serving from the ad-court (mostly at score 40:30), and with higher efficiency. I-formation reached higher efficiency than classical formation. We recommend using the I-formation more often in men’s doubles. I-formation and returning against I-formation are playing activities, that should be in good control by players and the players should practice these actions.
