The contributions to this book are the invited papers presented at the fifth annual Safety-critical Systems Symposium. They cover a broad spectrum of issues affecting safety, from a philosophical appraisal to technology transfer, from requirements analysis to assessment, from formal methods to artificial intelligence and psychological aspects. They touch on a number of industry sectors, but are restricted to none, for the essence of the event is the transfer of lessons and technologies between sectors. All address practical issues and of­ fer useful information and advice. Contributions from industrial authors provide evidence of both safety con­ sciousness and safety professionalism in industry. Smith's on safety analysis in air traffic control and Rivett's on assessment in the automotive industry are informative on current practice; Frith's thoughtful paper on artificial intelli­ gence in safety-critical systems reflects an understanding of questions which need to be resolved; Tomlinson's, Alvery's and Canning's papers report on collaborative projects, the first on results which emphasise the importance of human factors in system development, the second on the development and trial of a comprehensive tool set, and the third on experience in achieving tech­ nology transfer - something which is crucial to increasing safety.