Heart rate (HR) and rating of perceived exertion (RPE) are both recommended methods of determining exercise intensity for healthy adults. The purpose of this study was to determine how adult women self-select their exercise intensity during aerobic exercise. We interviewed 100 women exercisers who had been engaged regularly in an exercise program for at least 3 months to determine their method of gauging aerobic exercise intensity. Subjects exercised for about 45.1 +/- 21.4 minutes per session (4.4 +/- 1.4 times per week). The vast majority (84%) exclusively used self-selected effort perception to monitor their exercise intensity. Only 16% were familiar with an RPE chart. Although HR is touted heavily in fitness centers and on aerobic ergometers, self-selected effort perception (and not HR) is the method of choice by women who are experienced at aerobic exercise. It is recommended that fitness center personnel increase their efforts to educate the public regarding the appropriate use of effort perception as a method of gauging exercise intensity.