Conventional gait labs are limited in their ability to study running gait due to their size. There is no consensus in the literature regarding the ability to extrapolate results for adult treadmill running to overground. This comparison has not been studied in children. Twenty-four healthy children (mean age 11.7) ran overground at a slow running speed while motion capture, ground reaction force, and surface electromyography (EMG) data were obtained. The same data were then collected while participants ran for 6min on an instrumented treadmill at a speed similar to their overground speed. The kinematic, kinetic, and EMG data for overground and treadmill running were compared. Sagittal plane kinematics demonstrated similar hip and knee waveforms with the exception of more knee extension just before toe off. Ankle kinematic waveforms were similar during stance phase but treadmill running demonstrated decreased dorsiflexion during swing. Kinetic data was significantly different between the two conditions with treadmill running having a more anterior ground reaction force compared to overground. Due to the numerous differences between overground and treadmill gait demonstrated in this study, it is felt that the use of an instrumented treadmill is not a surrogate to the study of overground running in a pediatric population. This data set will function as a normative data set against which future treadmill studies can be compared.