The collective doses of ionizing radiation to Western populations have risen dramatically in the past three decades. Preliminary data on changes in radiation dose to the US population indicate that this increase has been driven largely by medical imaging, to which cardiovascular imaging modalities-such as nuclear stress testing, invasive coronary angiography, and cardiovascular CT-contribute greatly. Given the putative association between low-dose radiation exposure and cancer risk, which most experts agree is supported by the available evidence, the 'radiation issue' in medical imaging has garnered increasing interest. This opinion piece focuses on changes in the use of and doses from medical imaging, the relationship between radiation dose and cancer risk and the controversy surrounding this subject, and clinical implications of radiation exposure from imaging tests.