The objective of this study was to identify good practice in securing and using expert scientific advice for policy-making. Co-sponsored by eight government bodies, the study offered recommendations for improving the quality of scientific advice received by government and used in policy development. Although scientific methods are well established and scientific theories successfully inform policy decisions, this study was concerned with weak evidence, novel and incompletely known risks, hypotheses and gaps in data. On the basis of a literature review, case studies and informal interviews with a wide range of interested parties, a set of recommendations was formulated in the form of: principles—these are fundamental and comprehensive; a model process—the clearest way to secure scientific advice that is fully compatible with the principles; supplementary notes—these include detailed recommendations for some aspects of the process. The report, published by Health & Safety Executive, called for significant changes in the operation of existing mechanisms, which should result in more robust advice. This should lead to more informed policy decisions and a system of policy development with a higher level of public confidence and the support of the scientific community.