This investigation compared ratings of perceived exertion specific to the active muscles used during resistance exercise (RPE-AM) using the 15-category Borg scale during high-intensity (HIP) and low-intensity (LIP) weight lifting. Ten men (23.2 +/- 3.6 years) and 10 women (21.8 +/- 2.7 years) performed 2 trials consisting of seven exercises: bench press (BP), leg press, latissimus dorsi pull down, triceps press, biceps curl, shoulder press, and calf raise. The HIP and LIP protocols were completed in counterbalanced order. During HIP, subjects completed 5 repetitions using 90% of 1 repetition maximum (1RM). RPE-AM was measured after every repetition. During LIP, subjects completed 15 repetitions using 30% of 1RM. RPE-AM was measured after every third repetition. RPE-AMs were greater (p <or= 0.001) for HIP than for LIP for each exercise. For example, the mean initial BP RPE was 14.11 +/- 2.08 for the HIP and 8.34 +/- 1.35 for the LIP. Performing few repetitions using heavier weight is perceived to be more difficult than lifting comparatively lighter weight with more repetitions when external work is held constant.