The effect of exercise modality on the relationship between ratings of perceived exertion (RPE), blood lactate concentration, oxygen uptake (VO2), and heart rate (HR) was examined in 29 untrained male subjects who completed counterbalanced VO2max/lactate threshold (LT) protocols on a cycle ergometer (CE) and treadmill (TM). Heart rate, VO2, and RPE were determined at power outputs corresponding to LT and fixed blood lactate concentrations (FBLC) of 2.0, 2.5, and 4.0 mM and during maximal exercise. A repeated measures ANOVA indicated that, despite significant differences across exercise modality in HR and VO2 at LT, FBLC, and maximal exercise, no significant differences in RPE were found between exercise modalities during leg exercise. Mean (+/- SD) respective values for overall RPE at LT and FBLC of 2.0 mM, 2.5 mM, 4.0 mM, and max were 10.2 (2.2), 13.1 (2.1), 14.1 (2.3), 15.9 (2.3), and 18.8 (1.3) for the CE and 10.8 (1.9), 13.8 (1.8), 14.6 (1.6), 16.2 (2.6), and 18.5 (1.5) for the TM. It was concluded that exercise modality does not affect the perception of exertion at LT, FBLC, or maximal exercise and that a strong relationship exists between RPE and blood lactate concentrations.