As the surface areas of cities throughout the world become ever more congested/ and the quality of life deteriorates, those in authority are increasingly turning to the engineering use of created space underground. Transportation systems have been located at least partly underground for generations - particularly in London. Dozens of cities throughout the rest of the world are presently engaged in underground construction, not only for rail transportation schemes, but also for communications purposes, water supply, sewerage, roads, car parks, shopping centres, concert halls, museums and art galleries. Outside the cities underground construction continues to be used for hydro-electric purposes, gas storage, inter-city highways and rail systems, and for nuclear waste storage. This international engineering research study looks at the risks involved in underground construction, and in particular the nature of risks to people directly engaged on this work and to other persons who may be affected by the works and also looks at the nature of risks to the built and natural environment. The study brings together many details of past incidents and disasters that have occurred internationally, and from a broad analysis of the types and causes of failures of one type or another, looks to how such incidents may be prevented in the future. The identification and control of risk in underground engineering projects is seen as the duty and responsibility of all the main parties to the project - the client or promoter of the project, the engineering designers, and those chosen to undertake the construction work. Key components of a broad risk control strategy are described which are applicable regardless of the project's location or what the final purpose of the underground construction work might be. Within this study there are two international Case Studies to illustrate good and poor practice in the identification and control of risk in these types of projects.