Objectives:To investigate the validity and relative and absolute reliability of the Running Anaerobic Sprint Test (RAST) in amateur soccer players.Design: Cross-sectional experimental design with an element of repeated measures. Methods: Twenty three males completed the RAST on two occasions and a Wingate test (WAnT) as criterion measure of anaerobic power.Results: Criterion validity for the RAST was strong for peak power (r = 0.70, p < 0.001) and average power (r = 0.60, p = 0.002); however, the RAST significantly underestimated peak power compared to WAnT. The RAST showed very good relative reliability for average power, ICC = 0.88 and good relative reliability for peak power, ICC = 0.72. Assessment of absolute reliability highlighted that although when averaged across a group, test and re-test scores will be similar, when monitoring individuals an individual's retest score may range between 0.81 and 1.2 times the original value for peak power and between 0.9 and 1.16 for average power. Conclusion:The RAST is a practicable field test to estimate levels of average anaerobic power. However, the results show that the RAST is not sensitive enough to detect strongly individual changes below 20 % and is therefore not recommended to continually monitor an individual's anaerobic power. Also, if true measures of peak power are required the RAST test is limited.(Journal of Trainology 2016;5:24-29)