It is now a well-established tradition that every four years, at the end of winter, a group of 'celestial mechanicians' from all over the world gather in the Austrian Alps at the invitation of R. Dvorak. This time the colloquium was held at Badhofgastein from March 19 to March 25, 2000 and was devoted to the 'New Developments in the Dynamics of Planetary Systems'. The papers covered a large range of questions of current interest: t- oretical questions (resonances, KAM theory, transport, ... ) and questions about numerical tools (synthetic elements, indicators of chaos, ... ) were particularly well represented; of course planetary theories and Near Earth Objects were also quite popular. Three special lectures were delivered in honor of deceased colleagues whom, to our dismay, we will no longer meet at the 'Austrian Colloquia'. W. Jefferys delivered the Heinrich Eichhorn lecture on 'Statistics for the Twenty-first Century Astrometry', a topic on which Heinrich Eichhorn was a specialist. A. Roy delivered a lecture honoring Victor Szehebely on 'Lifting the Darkness: Science in the Third Millenium', in which in wove anecdotes and remembrances of Victor which moved the audience very much. A. Lemaitre spoke in honor of Michele Moons on 'Mech­ anism of Capture in External Resonance'. The end of her talk was devoted to a short and moving biography of Michele illustrated by many slides.

Statistics for Twenty-First Century Astrometry.- Synthetic Proper Elements for Outer Main Belt Asteroids.- Invariant Tori in the Secular Motions of the Three-Body Planetary Systems.- Improvements of Planetary Theories Over 6000 Years.- The Distribution of Energy Perturbations at Planetary Close Encounters.- Dynamics of Small Earth-Approachers on Low-Eccentricity Orbits and Implications for their Origins.- The Phase Space Structure Around L4 in the Restricted Three-Body Problem.- Why Do Trojan ASCS (not) Escape?.- The 2/1 and 3/2 Resonant Asteroid Motion: A Symplectic Mapping Approach.- Twist and Non-Twist Bifurcations in a System of Coupled Oscillators.- The Mel'nikov Subharmonic Function and the Non-Existence of Analytic Integrals in Non-Autonomous Systems.- On the Structure of Symplectic Mappings. The Fast Lyapunov Indicator: A Very Sensitive Tool.- Crossing of Various Cantori.- Fractal Dimensions as Chaos Indicators.- Normal Form Invariants Around Spin-Orbit Periodic Orbits.- The Third Integral in a Self-Consistent Galactic Model.- Counterrotating Galaxies and Memory of Cosmological Initial Conditions.- The Family P12 of the Three-Body Problem - The Simplest Family of Periodic Orbits, with Twelve Symmetries Per Period.- The Caledonian Symmetrical Double Binary Four-Body Problem I: Surfaces of Zero-Velocity using the Energy Integral.- Application of the Nonrestricted Three-bodies Problem to the Stellar System ? UMA.- Periodic Solutions of the Planetary 5:2 Resonance Three-body Problem.- Limits of Stability for Planets in Double Star Systems Using the Fast Lyapunov Indicators.- On a Fokker-Planck Approach to Asteroidal Transport.- Fractality in a Galactic Model.- Transformation Methods fo Trigonometric Parallaxes.- The Search for Exosolar systems.- The Two FixedCenters Problem Revisited.- The Phase Space Structure of the General Sitnikov Problem.