Summary Introduction: Aerobic fitness is changing under the influence of, among others, the level of training. Purpose of the work: The purpose of this study was to assess the level of development of the aerobic capacity of soccer players during the preparatory period. Material and method: Twenty-four players were tested at the beginning and at the end of the preparatory period. Group of respondents was in the age range 17 - 18 years. Trainings were held three - four times a week and a half - two hours. In the subjects, VO2max was assessed using the Astrand test. Results: Average VO2max at the beginning of the preparatory period was (49.11 ± 7.18) compared with the average value at the end (52.67 ± 6.58). A trend of increasing the oxygen ceiling after the preparatory period has been observed. Comparison of VO2max measured at the beginning of the preparatory period and at the end of the preparatory period did not show statistically significant differences (p = 0.077) Conclusions: For players who have been training for five years or more, we have observed high and very high values of the VO2max parameter. The preparatory period in the test run indicates a trend of increase of the VO2max, however difference in the value they are not statistically significant. It can be supposed that the level of training effect on the rate of growth VO2max assessed after the application of a three-month training oxygen. With the increase in the level of training the dynamics of increase of  the VO2max is getting slower.