The theme of ‘escape from metastable states’, either via noise-assisted hop- ping and/or quantum tunneling, is pivotal to many scientific disciplines. It impacts on suchdiversephysical,chemicalandbiologicalprocessesasdiffu- sion in solids, chemical reactions per se, nucleation phenomenaand transfer ofmatter and information in biologicalcomplexes, to name only a few. With ‘New Trends in Kramers’ Reaction Rate Theory’ this book fills yet another part of the multifaceted scope which underpins the Understanding of Chemical Reactivity. Since the publication of the comprehensive review about reaction rate theory in Rev. Mod. Phys. 52, 251 (1990) the field has witnessed many majordevelopments and extensions both in experiment and theory. In this book the focus will be on the theoretical progress. In doing so, the editorscollected aseries ofauthoritative articles from majorpractitioners in the field which as a whole give a representative- although notcomplete- sample ofthe novel recenttheoretical advances. As an inevitable consequence, the editors recognize that not all readers will wish to digest the volume in its entirety. We trust, however, that the reader will be able to choose from the many methods and techniques which he is interested in, and which he requires to perform his own new research in this area. There is the consistent underlying theme of noise-assisted barrier crossing that is running through all of the book. Nevertheless, each chapter should be considered as self contained. In this spirit the editors share the confident beliefthat the future research on the Kramers problem, and related topics, will be invigorated by the selectedcontributions herein.