Resting metabolic rate (RMR) of 22 individuals with Down syndrome was compared to that of 20 nondisabled control individuals of similar age (25.7 and 27.4 years, respectively). Using a ventilated hood system, we measured RMR in the early morning after an overnight fast. Peak aerobic capacity Volume of Oxygen (VO2 peak) and body composition were also determined. Resting metabolic rate was not different between groups. Adjusting RMR for body weight or body surface area did not change these findings. Using stepwise regression for the total population and each subgroup, we found that only body surface area was a significant predictor of RMR. These data show that individuals with Down syndrome do not have lower RMR than their nondisabled peers, suggesting that reduced RMR does not explain the high incidence of obesity in this population. [This study was supported in part by a grant from the American Heart Association and Grant H133040323 from the National Institute on Disability and Rehabilitation Research to the first author.]