[Purpose] The purpose of this study was to identify the most appropriate location of an accelerometer used for gait analysis. [Subjects] Fifteen healthy male volunteers participated in this study. [Methods] The trunk acceleration and ground reaction force (GRF) during normal walking were measured using an accelerometer attached at the level of the tenth thoracic vertebrae (Th10) and the third lumbar vertebrae (L3). The estimated GRF was calculated based on trunk acceleration. The maximum peak of GRF and the minimum peak were decided as the characteristic values, and it decided on the appearance times of the characteristic values as the characteristic times. The difference of the characteristic values and the characteristic times between GRF and estimated GRF were compared between 2 locations. [Results] The differences of the characteristic values of maximum peaks in the anterior-posterior direction at L3 were significantly smaller than that at Th10. The differences of the characteristic times of maximum peaks appearance in the vertical direction at L3 were significantly
smaller than that at Th10. [Conclusion] The pattern similar to GRF is obtained by the accelerometer attached at the L3.