Risk Matrices have long been adopted in parts of the systems safety community as a simple means of categorisation of risk, yet they are often developed and used incorrectly leading to confusion and poor safety management. This paper seeks to cut through to the essential elements and help the reader avoid the common pitfalls. It focuses on system safety risks to people, but could be similarly applied to environmental safety assessment too. Throughout this paper the term "Equipment” will be used to mean some item of plant, platform, process, system or indeed equipment within the boundary of study. The experiences recounted in this paper relate primarily to the application of risk matrices in the Defence industry but have, I believe, a wider relevance. The treatment of topics surrounding risk matrices in the paper are not intended to be comprehensive; simply sufficient to keep the central subject matter of risk matrix development in context.