Falls are the leading cause of unintentional injuries in the elderly in Taiwan and many industrial countries, and commonly occur at home. To reduced fall-related socioeconomic cost, the goal of this study is to identify suitable floor materials on which the elderly could have stable gait. We tried to quantify the gait stability under different floor conditions in this paper. Six healthy subjects (aged 20-23 yrs) have been tested. A six-camera motion capture system and two force platforms were used to obtain kinematics and kinetics of whole body during gait on different floor conditions. In consistent conditions (same floor materials on the whole walkway), the lower the coefficient of friction (COF) of the floor material, the smaller values of cadence and required COF (RCOF) under subjects' feet, and the larger values of gait stability-related variables, such as stance time, stride time, and step width, during walking at self-selected comfortable speed (p<0.05). As compared with the consistent conditions, walking from a material with higher COF to another with lower COF would induce larger ankle dorsi/plantar-flexion angle at heel contact. In addition, the peak RCOF during the stance phase was higher after the floor material change. The results of this study suggest that double support time, stride velocity, and mean gait velocity might be good indicators of gait stability. Walking from one floor material to another with lower COF may induce higher risk of falls than walking on a floor with consistent materials. Therefore, avoiding or using caution, especially for the elderly, when walking from one floor material to another with lower-COF is suggested.