This paper addresses the topic of failures in computer-based systems. It does so in three stages: first it describes failure cases in a single domain, that of computer-based ambulance despatch systems; then it discusses some of the features of those cases; finally it considers the importance of reporting and analysing failures, in order to discover their causes and to learn lessons that will help eliminate those causes of failure in the future. Failure, it is argued, provides a valuable learning opportunity that may lead, when recognized, to better practice and future success. Copyright © 2003 John Wiley & Sons, Ltd