The purpose of this graduate thesis was to determine whether there is significant differences in reaction time and split-step movement jump between two groups of analysed professional ATP players (n = 20; age = 28 +/- 9; body mass = 78 +/- 12 kg; and body height = 188 +/- 12 cm). The players were separated in two groups. First group (from 1. to 10. player on ATP list) and second group (from 100. to 110. player on ATP list). The goal was to determine deviations from reaction time and split-step jump between first and the second group in three variables that were analysed. First was the split-step after the service in retern of the serve and between groundstrokes. Contact of the ball with opponent's racket was observed, and in that point the split-step of player's was analysed. If the player was not in ideal split-step position the deviations were determined. Research showed, that there is a statistically significant difference between arithmetic means between two groups in variables – serve, with certain error (p < 0,01). With variable retern results shown statistically significant difference between arithmetic means with certain error (p < 0,00), as well with variable for groundstrokes with certain error (p < 0,01). It shows that split-step is crucial technical and tactical element and quality of split-step execution can show differences between higher and lower ranked professional ATP players. Because of that it is important that split-step must be taught from early stages of tennis development in children.