Williams, MD, Wiltshire, HD, Lorenzen, C, Wilson, CJ, Meehan, DL, and Cicioni Kolsky, DJ. Reliability of the Ekblom soccer-specific endurance test. J Strength Cond Res 23(5): 1378-1382, 2009-The aim of this study was to explore and quantify measurement reliability of the Ekblom endurance test. Experienced university soccer players (n = 19; age = 20.5 ± 2.5 years; mass = 80.4 ± 9.8 kg; and stature = 179.0 ± 6.0 cm) completed the Ekblom endurance test on 3 separate occasions. Time to complete trial 1 (549 ± 26 seconds) and trial 2 (547 ± 26 seconds) was analyzed, and despite no significant difference (F1,18 = 4.119, p = 0.057, ηP2 = 0.186) between trials, some evidence of systematic bias was observed in the data. Therefore, trial 2 data were compared with those of trial 3 (548 ± 27 seconds), with trial 1 data removed. The subsequent analysis (F1,18 = 0.740, p = 0.401, ηP2 = 0.039) showed a reduction in the risk of making a type II error when compared with the previous analysis. From the reliability analyses (3,1 intraclass correlation = 0.983, SEM = ±3 seconds, smallest worthwhile change = 5 seconds, standard error of prediction [95% confidence intervals] = ± 9 seconds), a high level of measurement reliability was observed and the sensitivity of the test to monitor changes was “good.” In summary, it was shown that a test that involves a variety of soccer-specific forms of locomotion can be highly reliable and sensitive to detect change. In light of the systematic bias found, we do, however, recommend a familiarization session to be scheduled before the introduction of this test.