This paper discusses the importance of a nontumbling gait, a gait that allows preventing complete tumbling of the robot.〓Nontumbling gait ismade possible by the effect of the swing leg whichmay contact the ground even when the robot is affected by an〓external disturbance. Such an effect is present in both static walking and dynamic walking. Stability criterion required to maintain〓the nontumbling gait is then considered and proposed through generalized directional normalized energy stability margin. The〓validity of the introduced criterion is evaluated by a tumbling experiment with a simplified walking robot model.The concept is〓also applied to the gait control of the newly developed walking robot TITAN-XIII.