Santos, GAd, Numata-Filho, ES, Rosa, TdS, Passos Neves, RV, Simões, HG, and Moreira, SR. Anaerobic threshold determination in cycle ergometer from rating of perceived exertion. J Strength Cond Res 36(5): 1277–1281, 2022—The objective of the study was to investigate the validity of the rating of perceived exertion threshold (TRPE) for anaerobic threshold (AT) estimation during an incremental test (IT) on a cycle ergometer. Nineteen physically active and healthy men performed an IT on a cycle ergometer. The intensity corresponding to the AT was considered as the point immediately before the abrupt increase in blood lactate concentration ([La]) in the IT. TRPE was determined in the last intensity corresponding to perceptual response previous the 15 arbitrary units (AU) in the 15-point RPE scale. The heart rate (HR), [La], and RPE were obtained at the end of each stage of the IT. There was no significant difference between workload obtained from the AT (150 [120–150] watts) and TRPE (150 [120–150] watts) (p > 0.05). In addition, there were no differences between HR (AT, 139.5 ± 12.7 b·min−1 vs. TRPE, 141.9 ± 14.6 b·min−1, p > 0.05) and [La] (AT, 3.1 [2.8–3.2] mM vs. TRPE, 3.1 [2.9–3.7] mM, p > 0.05). There was a strong correlation between the intensities in AT and TRPE during the IT (r = 0.88). A substantial reliability (intraclass correlation coefficient = 0.84 [0.64–0.94 confidence interval 95%]) was evidenced, as well as a substantial agreement between the AT and TRPE intensities (Pc = 0.84), as confirmed by the Bland-Altman plot (−4.7 [−34.2/24.7]). TRPE was a predictor of the AT (β = 1.146, R = 0.770, SEE = 15.070, p < 0.01). It can be concluded that TRPE is valid for AT estimation during an IT on a cycle ergometer.