The primal goal of this study was to measure the anaerobic power output by Margaria-Kalamen test and to determine the differences between the four age categories of basketball players of the basketball club „Virka“ from Virovitica. The survey was conducted on a sample of 40 respondents performing in four age categories: M-15 (n = 10; age: 13.7 ± 0.46; body weight 62.1 kg ± 12.71 kg; height 175.4 cm ± 7.8 cm), M-17 (n = 10; age: 15.7 ± 0.48; body weight 75.7 kg ± 8.1 kg; height 188 cm ± 4.45 cm), M-19 (n = 10; age: 17.6 ± 0.52; body weight 77.2 kg ± 13.9 kg, height 188,8 cm ± 8,9 cm); SENIORS (n = 10; age: 27.5 ± 5.17; body weight 91.9 kg ± 10.6 kg, height 192.3 cm ± 7.7 cm). The condition of inclusion in the research was that basketball players were active competitors in certain age categories. In addition to measuring basic anthropological characteristics such as height and body weight, subject measured the strength assessed by Margaria-Kalamen test and the time it took a subject to run between the third and ninth stair when performing the test. The assumption is that the age of the respondents significantly affects the results of the Margaria-Kalamen test, where the older subjects have significantly better results than the younger. The results showed that the group M-15 has the best average time of the Margaria-Kalamen test (0.53 ± 0.05 s), while the SENIORS achieved the best results in the anaerobic power output (1556.2 ± 142.49 W).