— We present here a concept and realization of a dynamic walker that is stabilized by using a fast and heavy rotor, a gyro. The dynamics of a symmetric, fast rotating gyro is different from that of a non-rotating solid body, e.g. in the case of small disturbances it tends to stabilize the axis. This property is used and tested in a passive dynamic walker. We investigate the stability of a knee-less walker that is stabilized by a gyro in a 3D environment, and present also simulations. As the result of this work we show that the rotor enhances the stability of the walking in the simulations. We also summarize some concepts and simulations of actuated robots with a gyro. Finally we give an overview of experiments and prototypes that are realized so far.