Deep fear of nuclear radiation is widespread, yet research on radiation’s biological effects finds that the level of alarm far exceeds the actual danger. This “radiophobia” has roots in the fear of nuclear weapons, but has been significantly reinforced and inflamed by accidents at nuclear power plants. Radiophobia does far more harm to human health than the radiation released by nuclear accidents. In some cases, the harm results from disaster response. The influence of radiophobia on society’s energy choices poses great additional dangers.