How dangerous is low level radiation?

Problems in the theoretical basis for the linear-no threshold theory of radiation carcinogenesis are reviewed, and it is shown that they very strongly suggest that the theory greatly overestimates the risk of low level radiation. A direct test of the theory, based on the radon-lung cancer relationship is described; it strongly reinforces that conclusion. However, it is shown that even if the linear-no threshold theory is valid, the public's fear of low level radiation, at least in some contexts, is grossly exaggerated.