Purpose: The 30-s Wingate Anaerobic Test (WAnT) has been used to assess anaerobic performance capacity and to evaluate physiological responses to supramaximal exercise. Blood lactate concentration ([La]) following supramaximal exercise is often used in the field and in the laboratory to assess the glycolytic contribution to exercise. Although the reliability of the performance in the WAnT has been established, this has not been the case with the WAnT's [La] response. Thus, the main purpose of this research was to study the test-retest reliability of peak [La] following the WAnT. Additionally, the test-retest reliability of the heart rate (HR) and plasma volume changes (Delta PV) response was also evaluated. Methods: Twenty-nine subjects (15 male, 14 female) of diverse training levels as well as physical characteristics (mean +/- SD: 23.3 +/- 7.0 yr, 62.5 +/- 12.0 kg, 170.8 +/- 9.7 cm, and 16.3 +/- 6.2% fat) performed two WAnTs within 1 wk. Capillary blood was sampled from a prewarmed fingertip at rest just before the WAnT and at 3, 5, 7, and 9 min following it. HR was also measured during these times. Results: Mean-power (MP) (+/-SE) in test 1 and test 2 was 8.4 +/- 0.2 and 8.3 +/- 0.2 W.kg(-1) body mass, respectively. Peak [La] was attained 5-7 min following the WAnTs and was nor significantly different between test 1 and test 2 (9.7 +/- 0.3 vs 9.8 +/- 0.3 mM, respectively). Peak HR occurred within 5 s post-WAnT and was not different between tests (170.8 +/- 2.2 and 171.3 +/- 2.2 beats.min(-1) in test 1 and test 2, respectively). Peak Delta PV was not different between tests (-12.0 +/- 3.4 and -11.1 +/- 3.2%, in rest 1 and test 2, respectively). The intraclass reliability coefficients for peak [La]. peak HR and Delta PV were 0.926, 0.941, and 0.878, respectively, whereas the corresponding value for MP was 0.982. Conclusions: We conclude that peak [La], peak HR, and Delta PV following me WAnT are reliable measures.