This study examined habituation to treadmill walking or running in children. Twenty-four boys and girls, ages 7–11, completed six 6-min trials of treadmill exercise at one of these speeds: (a) comfortable walking pace (CWP), (b) CWP + 15%, (c) running at CWP + 3 km·hr⁻¹, or (d) running as above + 15%. The six trials were repeated in a second visit. The a priori criterion for habituation was a decrease in steady state values of oxygen uptake (V̇O₂), heart rate (HR), respiratory exchange ratio (RER), and stride rate (SR) or an increase in stride length (SL) and hip joint vertical amplitude (HA) from one trial to the next. There was no consistent pattern indicating habituation for the group. Many trials and more than one day of testing do not appear to improve the stability of the metabolic or kinematic variables. The lack of consistency in individual responses suggests that monitoring subjects’ habituation individually is important.