Ambiguous findings have been reported in previous studies concerning the relationships between resting metabolic rate (RMR), effects of exercise, and race in postmenopausal women. The purposes of this study were (1) to determine the effect of exercise training on RMR in postmenopausal women and (2) to determine whether this effect is different by race. We analyzed data from 24 African American (AA) (age, 56.3 +/- 5.0 years) and 23 Caucasian (CA) (age, 58.6 +/- 6.1 years) women. RMR was measured by indirect calorimetry after an overnight fast. Subjects completed tests of maximal exercise with metabolic measurements, waist to hip ratio, and body composition. At the completion of all tests, each subject was randomly assigned to either the exercise training or the control group. Aerobic exercise was performed 3 to 4 days per week for 6 months. Intensity was set at 70% to 85% maximal heart rate for 45 to 60 minutes per session. Both AA and CA exercise groups had a significant decrease (P < .05) in body weight (kilograms), percent body fat, and body mass index (BMI) and an increase in aerobic capacity, whereas the control groups did not change. There were no race effects. AA women exhibited significantly lower values than CA women for measured RMR (P < .05). The RMR (kilojoules) of the AA women (both control and exercise groups) decreased over time (P < .05), whereas the RMR of the CA women did not change. Adjusting RMR for BMI or for changes in lean body mass and fat mass did not alter these results. In conclusion, this 6-month endurance-training program did not affect RMR in these postmenopausal women, as RMR did not change in CA women, but decreased significantly over time in both groups of AA women. The factors that contribute to these findings should be the focus of future studies.