The assessment of risks and the control of site safety are becoming increasingly important. The observational method provides a means of controlling safety and minimizing costs by the modification of design during the construction process. Before construction commences the limits of behaviour which are acceptable and the range of possible behaviour are established. A method of monitoring is devised and contingency plans are made that can be implemented if the acceptable range is exceeded. This method is accepted in design codes, such as the draft Eurocodes and the Hong Kong guide to retaining walls. The papers in this volume were assembled by the British Geotechnical Society, and provide a grounding in all aspects of the observational method in geotechnical engineering. It includes a record of discussion on the papers at a meeting held by the British Geotechnical Society.