It has been shown that a high level of aerobic fitness is important for athletes participating in intermittent (team) sports. The majority of studies investigating the effects of traditional and sport-specific aerobic interval exercise on physiological measures and performance have involved field-based team sports. In some instances the effectiveness of sport-specific aerobic training has been questioned. To date, no study has investigated the influence of a sport-specific training approach in the sport of basketball. Purpose: The aim of the present study was to evaluate the effectiveness of a basketball specific endurance circuit on improving measures of aerobic fitness. Methods: Ten male high school basketball players, age 16.4 ± 1.2 years, ranked by fitness level and randomly assigned to a training group (N = 6) or control group (N = 4) participated in the study. The sport-specific aerobic endurance training replaced the fitness component of regular training and was performed during the competitive season. The sport-specific training consisted of interval training using a basketball specific endurance circuit, four times 4 min at 90-95% HRpeak with a 3 min recovery at 60-70% HRpeak, twice per week for 6 weeks. During this time the control group performed regular basketball training. Results: For both the training and control groups the actual mean training intensity for total training duration were 77.4 ± 2.9% HRpeak and 74.1 ± 6.7% HRpeak, respectively. The actual mean training intensity during the work intervals in the training group was 84.1 ± 2.3% HRpeak. There were no clear differences between effects of the two training approaches for measures of maximal oxygen uptake (3.3%; 90% confidence limits, ± 19.3%), running economy (-3.3%; 90% confidence limits, ± 14.2%), repeated sprint ability (0.6%; 90% confidence limits, ± 5.7%) and anaerobic power maintenance during the repeated sprints (-13.7%; 90% confidence limits, ± 49.0%). However, a clear non-trivial effect on sub-maximal heart rate was observed (-7.3%; 90% confidence limits, ± 2.0%) suggesting a beneficial training effect after training. Some evidence for attenuation of speed (-1.8 to -2.8%; 90% confidence limits, ± 3.4 to 5.7%) and power (-1.7%; 90% confidence limits, ± 17.1%) was apparent. Conclusion: Although clear changes in sub-maximal HR responses were observed in the training group, the data in the present study suggests that a basketball specific endurance circuit has little effect on other laboratory and field-based measures of aerobic fitness. In fact, the basketball specific endurance circuit may lead to reduced improvements in jumping and sprinting performances. Further research is required to clarify the effect of aerobic training approaches on basketball-specific fitness and performance.