The role of radiology has expanded from diagnosis and treatment of individual patients to disease surveillance and prevention at the population level. This chapter introduces a collection of definitions of public health and then describes its link with radiology using selected evidences. Digitization of health information, especially imaging studies, is the key change of concept of radiology from an independent entity to one that is interconnected with a broad range of public health entities. Specific examples include radiological screening technologies for breast, colorectal, and lung cancers as well as infectious diseases like tuberculosis. Also discussed is the relationship between radiology and the health of the public with emphasis on radiation safety.