People perceive different types of radiation risks in very different ways. Surveys of the general public in the United States and elsewhere have consistently shown that people perceive nuclear power and nuclear waste as having high risk, but perceive other sources of radioactivity—such as medical x-rays and naturally occurring radon gas—as posing much lower risk. The majority of radiation experts see things quite differently, rating nuclear power and nuclear waste as less risky than the general public does, and perceiving medical x-rays and radon as more risky than generally believed. This perception gap demonstrates that acceptance of risk is conditioned by a number of factors, such as trust in the managers of the technology and appreciation for the direct personal benefits of the technology. Risk-communication strategies that help people place the risks of nuclear power and nuclear waste in perspective by comparing them with other risks can help reduce fears of radiation. Education about radiation can also affect risk perceptions and attitudes. Although differences between the perceptions of laypersons and those of experts cannot be attributed in any simple way to degree of knowledge, it is clear that better information about radiation and its consequences is needed. There is a particularly urgent need to develop plans and materials for communicating with the public in the event of a radiological disaster. The fear, anger, and distrust following the accident at Fukushima shows that communication is still a major problem.