The scientific community is increasingly being called upon to provide evidence and advice to government policy-makers across a range of issues, from short-term public health emergencies through to longer-term challenges, such as population ageing or climate change. Such advice can be a valuable, or even essential, input to sound policy-making but its impact depends on how it is formulated and communicated as well as how it is perceived by its target policy audience and by other interested parties. It is rare that scientific evidence is the only consideration in a policy decision and, particularly for complex issues; many interests may have to be balanced in situations where the science itself may be uncertain. The rapid evolution of information and communication technologies and moves towards more participative democratic decision-making have put additional pressure on science to help provide answers and solutions, whilst also opening up the academic enterprise to closer surveillance and criticism. What used to be ‘private’ debates between different scientific viewpoints over areas of uncertainty have now become public disputes that can be exploited by different stakeholders to confirm or deny entrenched positions. Science is truly at the centre of many important policy issues and scientists are increasingly visible and, in many cases, increasingly vulnerable, in policy-making processes.