This Volume is the Proceedings oft the IUTAM Symposium on Mesoscopic Dynamics of Fracture Process and Materials Strength, held at Osaka in 2003. It contains 41 papers by acknowledged experts covering innovative researches in the current solid mechanics field. The material deals with several topics related: Discrete Dislocation Dynamics; Dislocation Patterning; Large-scaled Molecular Dynamics Simulations; Ab-initio Calculations; Multiscale Modeling of Plasticity; Concurrent Modeling coupled with Finite Element Method; Crystal Plasticity; Fracture and Deformation Problems of Amorphous Materials, Semiconductor Materials and Nano-crystalline Materials. This volume will be of interest to research workers and graduate course students in theoretical and computational solid mechanics. In particular, those engaged in developing computational schemes and modeling the strongly scale-dependent phenomena, will find some of their current problems considered in this volume.