This book presents a collection of fifteen high quality selected papers from the 2007 edition of the ECCOMAS Thematic Conference in Multibody Dynamics, which was held June 25-28 at the Politecnico di Milano, in Milan, Italy. The purpose of this collection is to provide the international multibody dynamics community with an up-to-date view on the state of the art in this rapidly growing field of research which now plays a central role in the modeling, analysis, simulation and optimization of mechanical systems in a variety of fields and for a wide range of industrial applications. The book will be of interest to engineers working on any one of the many aspects of modern multibody dynamics who want to be informed by some of the leading experts in the field on the principal research directions, recent achievements and the most challenging successful applications.