It is well known that exercise plays an important role in a weight management program. However, exercise prescription for sedentary, overweight individuals poses a difficult task. The ACSM Guidelines (5th edition, 1995) suggest a RPE range of 12-16 (Borg 6-20 scale) for exercise prescription. The purpose of this study was to examine the relationship between RPE, exercising heart rate and VO2 in 40 obese women whose mean age, weight, height and percent fat were 42±8 yrs, 88.2 ± 12 kg. 165±7 cm, and 47.7±4% fat, respectively. Subjects completed a submaximal cycle ergometer test at 0, 25. and 50 watts. Steady state heart rates (HR), VO2, and RPE were recorded at the end of each 3-minute workload. RPE was not related to% max heart rate at any workload(r's ranged from 0.03 to 0.16). Furthermore, RPE was not significantly related to% VO2 peak at any workload (r's ranged from 0.24 to 0.28). Results (mean ± SD) were as follows:Table When HR was at 60 ± 5% of HR max only 33% of the RPEs were between 12 and 16, with the remainder rating the effort less than 12. When HR was at 80 ± 5% of HR max, 56% of the RPEs were between 12 and 16, 41% rated the effort less than 12, and 3% rated it greater than 16. These data suggest that RPE is not a valid method to prescribe exercise intensity for sedentary, overweight women. Future research should examine whether RPE is an appropriate tool for exercise prescription after subjects are introduced to exercise and body weight is reduced.