OBJECTIVES: Yo-Yo intermittent endurance test is a popular method to evaluate aerobic cacpacity and train physical fitness in soccer players. However, few studies related to Yo-Yo test were found in amateur and basketball players. The purpose of this study is to investigate the characters and related factors upon the performance of Yo-Yo intermittent endurance test in middle school basketball players of Macau. METHODS: 38 middle school basketball players including 14 forwards, 8 centrals and 16 backwards, aged 14 – 19 years old, had never taken “Yo-Yo” test before and were recruited to participate in this study voluntarily. Training years and training time each week were 5.32  1.19 (2 - 7) yr and 5.82  1.25 (4 - 9) hours respectively. Every player should complete a maximal treadmill exercise test with Bruce protocol to estimate maximal oxygen uptake ( O2max), and Yo-Yo tests twice. RESULTS: It was found that there were no differences among forwards, centrals and backwards in Yo-Yo performance. The Yo-Yo performance was not affected by age, training history (years), field situations and percentage of body fat (PBF, %), but by O2max and training hours per week in amateur basketball players (Table 1). CONCLUSION: It suggests that Yo-Yo Intermittent Endurance Test is mainly determined by aerobic endurance in amateur basketball players. Training hours per week is an influencing factor of shuttle running capacity in Macau middle school basketball players.