This book constitutes the final report of the work carried out in the project KORSO ("Korrekte Software") funded by the German Federal Ministry for Research and Technology. KORSO is an evolutionary, prototype-oriented project aimed at improving the theoretical foundations of quality-driven software engineering and at implementing known techniques for applications of practical relevance. The 21 strictly refereed papers presented are organized in five sections on methods for correctness, languages, development systems and logical frameworks, tools, and case studies. In addition, the preface and introductory paper give valuable background information and a concise state-of-the-art overview.