Castagna, C, Lorenzo, F, Krustrup, P, Fernandes-da-Silva, J, Póvoas, SCA, Bernardini, A, and D'Ottavio, S. Reliability characteristics and applicability of a repeated sprint ability test in young male soccer players. J Strength Cond Res 32(6): 1538-1544, 2018-The aim of this study was to examine the usefulness and reliability characteristics of a repeated sprint ability test considering 5 line sprints of 30 m interspersed with 30 seconds of active recovery in nonelite, outfield, young, male soccer players. Twenty-six (age, 14.9 ± 1.2 years; height, 1.72 ± 0.12 cm; body mass, 62.2 ± 5.1 kg) players were tested 48 hours and 7 days apart for 5 × 30-m performance over 5 trials (T1-T5). Short-term (T1-T2) and long-term (T1-T3-T4-T5) reliabilities were assessed with intraclass correlation coefficient (ICC) and with typical error for measurement (TEM). Short- and long-term reliability ICCs and TEMs for total sprint time and best sprint performance were nearly perfect and satisfactory, respectively. Usefulness (as smallest worthwhile change and TEM ratio) resulted acceptable (i.e., = 1) and good (i.e., >1) for total sprint time and best sprint performance, respectively. The present study revealed that the 5 × 30-m sprint test is a reliable field test in short and long terms when the sum of sprint times and the best sprint performance are considered as outcome variables. Sprint performance decrements variables showed large variability across trials.