This project addresses major problems related to the design and control of legged robots, essentially of biped type. One of the main research issues concerns the computer aided design of robot controllers handling reactivity and real-time aspects. In that framework, problems of specification, programming and formal verification at the task level have been considered and validated on various examples. Concerning the more specific aspect of biped robots, studies are conducted on several topics : modelling of human locomotion, in order to select the pertinent variables to be used in the control ; theoretical study of impact effects, optimal control design and simulation analysis of a compass-like robot, control of a biped robot using the task function approach. The project has also an activity on sensor-based control, especially on visual servoing. Finally, let us mention that a large study is starting, which is aimed at the physical realization of a 16 degrees-of-freedom biped system and of its controller, which would walk in a human-like way on plane terrains and stairs. Many of these researches are conducted in cooperation with other laboratories.