Chaotic behaviour in the solar system is very often connected with resonance. Great progresses have been made in the last few years to relate the existence of the Kirkwood gaps with chaos. Uses of mappings have allowed cheap computations over millions of years. Unexpected intermittent increase of orbital eccentricities due to the existence of thin chaotic zone provides a mechanism for planetary close approach. However semi-analytical developments show that at least for the 2/1 resonance the problem remains open. Chaotic rotations of satellites like Hyperion or Miranda and chaotic motion of comets in nearly parabolic orbits are predicted and some physical implications discussed. Both comet Halley and Hyperion appear to be good candidates for real examples of dynamical chaos in the solar system.
Recent work on resonant motion in the Solar System and in planetary system is presented in a unified way. The physical models used and the underlying mathematical theory is also presented. The relation between resonance and instabiity is studied and the mechanism of generation of instability is discussed and is related to the various parameters of the system.