The objective of this study was to investigate the effect of an 8-week aerobic-exercise training program on ventilatory threshold and ventilatory efficiency in overweight children. Twenty overweight children (BMI > 85th percentile) performed a graded cycle exercise test at baseline and were then randomly assigned to 8 weeks of stationary cycling (n = 10) or a nonexercising control group (n = 10). Ventilatory variables were examined at ventilatory threshold (VT), which was determined via the Dmax method. After 8 weeks, significant improvements occurred in the exercise group compared with the control group for oxygen uptake at VT (exercise = 1.03 +/- 0.13 to 1.32 +/- 0.12 L/min vs. control = 1.20 +/- 0.10 to 1.11 +/- 0.10 L/min, p < .05) and ventilatory equivalent of carbon dioxide (VE/VCO2) at VT (exercise = 32.8 +/- 0.80 to 31.0 +/- 0.53 vs. control = 30.3 +/- 0.88 to 31.7 +/- 0.91, p < .05). Aerobic-exercise training might help reverse the decrements in cardiopulmonary function observed over time in overweight children.