These proceedings include tutorials and papers presented at the Sixth CSR Confer­ ence on the topic of Large Software Systems. The aim of the Conference was to identify solutions to the problems of developing and maintaining large software systems, based on approaches which are currently being undertaken by software practitioners. These proceedings are intended to make these solutions more widely available to the software industry. The papers from software practitioners describe: • important working systems, highlighting their problems and successes; • techniques for large system development and maintenance, including project management, quality management, incremental delivery, system security, in­ dependent V & V, and reverse engineering. In addition, academic and industrial researchers discuss the practical impact of current research in formal methods, object-oriented design and advanced environ­ ments. The keynote paper is provided by Professor Brian Warboys of ICL and the University of Manchester, who masterminded the development of the ICL VME Operating System, and the production of the first database-driven software en­ gineering environment (CADES). The proceedings commence with reports of the two tutorial sessions which preceded the conference: • Professor Keith Bennett of the Centre for Software Maintenance at Durham University on Software Maintenance; • Professor John McDermid of the University of York on Systems Engineering Environments for High Integrity Systems. The remaining papers deal with reports on existing systems (starting with Professor Warboys' keynote paper), approaches to large systems development, methods for large systems maintenance and the expected impact of current research.