A paucity of data exists related to the usefulness of Ratings of Perceived Exertion (RPE) to set exercise intensity in non-laboratory settings. The purpose of this study was to determine if RPE could be used on an outdoor track to generate blood lactate and heart rate (HR) responses similar to those obtained on a treadmill (tm) run. Nine experienced runners (6 males, 3 females; [Formula: see text]) completed a horizontal, incremental tm test. HR, RPE, and lactate were measured for each stage. Subsequently, subjects ran for 30 min on an outdoor track at the RPE corresponding with 2.5 mM lactate during the tm run. Repeated measures ANOVA compared lactate and HR values at 2.5 mM lactate on the tm run and values obtained during the track run. Lactate during the track run was significantly higher (p < .05) than 2.5 mM throughout the 30 min (6.9 ± 2.9, 63 ± 2.9, and 5.8 ± 3.0 mM at 10, 20, and 30 min, respectively). HR at 2.5 mM lactate during the tm run (173 ± 6.1 bpm) was significantly lower (p < .05) than at min 10 and 20 of the track run (182.6 ± 9.3 and 182.9 ± 8.0 bpm, respectively) but not different from min 30 (181.3 ± 10.6 bpm). In summary, it is difficult to generate specific physiological responses using RPE. Key words: RPE, Borg Scale, exercise, lactate, training