Monitoring is a subject of particular importance to underground construction works. It is often a key risk mitigation measure both for the control of the construction process and the protection of existing assets affected by excavations. The subject is treated at the level of key principles, focusing on objective setting, strategic planning and the high level specification of monitoring systems. It aims to help avoid problems, which have in the past arisen due to omissions in these areas. This guide is structured to reflect the key stages in a project. It starts with objective setting and then addresses requirements for system planning, specification, design, operation and management. It also seeks to highlight the roles and responsibilities of the various stakeholders at each stage. Five illustrative case studies taken from a range of projects of different scales highlight the critical role of strategic and well-planned monitoring programmes in the success of any underground construction project.