Recent years have seen an increased awareness of the importance of public engagement with science and technology (S&T). The science to be funded, how it should be carried out and how it should be used and regulated are all debated questions. But what is meant by public engagement? Can public engagement in policy be effectively achieved without a wider dialogue between scientists and the public? How have methods of public engagement developed, and at what stage in the S&T process are they best applied? How do policy-makers take into account public opinion when using and regulating S&T?