This series aims to report, interpret and evaluate progress in the field of quantum chemistry. Over the course of several years, the series has treated the many facets of chemical physics and is designed to function as an essential reference and guide to further progress. For each volume, the editor selects topics within chemical physics and invites an expert to write a comprehensive article. Volume 69 presents a review of recent developments in ab initio methods in quantum chemistry, covering the applied aspects. Reviews from experts in these areas are included.