Stable and robust autonomous dynamic locomotion is demonstrated experimentally in a four and a six-legged robot. The Scout II quadruped runs on flat ground in a bounding gait, and was motivated by an effort to understand the minimal mechanical design and control complexity for dynamically stable locomotion. The RHex 0 hexapod runs dynamically in a tripod gait over flat and badly broken terrain. Its design and control was motivated by a collaboration of roboticists, biologists, and mathematicians, in an attempt to capture specific biomechanical locomotion principles. Both robots share some basic features: Compliant legs, each with only one actuated degree of freedom, and reliance on (task space) open loop controllers.