Title: The measurement of the reactive time of czech elite tennis players in the junior category 15 - 19 years old. Objectives: The object of this thesis is to measure reactive time of elite tennis players, to determine mutual relations of specific factors. Methods: Research of a literature, questionnairies and people testing Result: In theoretical part, our thesis offers way how to improve reactive time in the way how scientific researches documents it. We focused on a testing of a reactive time of players in category of juniors in a practical part. The main requirement was to be within 30th place on the czech ranking. We tested these players on a simple and complicated subjects by the Vienna test system. Our research proved the dependence of the tennis on the reactive periode and the motoric reaction. Majority of probands was placed on a border above 84% of the population sample which was considered as a very outstanding result. We also proved that if are players influenced by permanent training of a reactive time their performance is improved. Key words: tennis, reactive time