The purpose of this study was to compare an objective measurement of smoothness between a group of runners and a group of non-runners during running and fast walking. Smoothness was quantified by evaluating the endpoint jerk-cost (JC) at the heel. Subjects walked at a speed of 1.75 m.s(-1) and ran at a speed of 3.35 m.s(-1) on a motor driven treadmill while 2-D kinematic data (60 Hz) were collected from a sagittal plane view. The runners were found to be smoother than the non-runners during both gait conditions, suggesting that this group was inherently smoother in gait related tasks. This study demonstrated that the smoothness of gait can be quantified objectively by evaluating the end-point JC at the heel, and that competitive runners tend to exhibit smoother strides than recreational runners during both running and fast walking.