There has, until recently, been a utopian belief in the benefits that science can bring. Scientists often claim that their insights are objective and can provide answers to real problems, but it was only in the twentieth century that their achievements matched their ambitions. During the Second World War scientists and engineers mobilised on an unprecedented scale, researching, developing and using technologies only dreamed of a few years earlier. On the back of this wave of technical progress, the reputations of scientists and engineers rode high and grateful governments rewarded them with generous funding for research and new facilities. Governments – and the general public – were encouraged to believe that many more benefits would flow if scientific research continued to flourish. But as science transformed daily life, people began to realise its limitations and started to question decisions made on the basis of scientific methods. Now governments find that people are no longer willing to accept ‘scientific’ answers to policy issues. To illustrate how public opinion can affect scientifically based government policy, we look at three examples: nuclear power, foot and mouth disease, and genetically modified food.