OBJECTIVES: Rapidly increasing use of imaging procedures in Canada and the United States has raised concerns about exposure to low-dose ionizing radiation in the general population. We assessed radiation exposure from medical and non-medical uses. METHODS: Recent evidence-based studies linked exposure to low-dose, ionizing radiation with the development of cancer/leukemia. Individuals at risk for repeated radiation exposure (in health care/nuclear industry) are typically monitored and restricted to effective doses of 20-50 mSv per year.  In contrast, radiation exposure in the general population is not monitored. Using the epidemiological databases from Canada and the United States, we are developing an age/sex stratified population model to assess radiation exposure from medical and non-medical uses. We identify the potentially most exposed subpopulations, for which the long-term risks are most relevant. RESULTS: We compiled the list of effective doses (mSv) from radiation exposure for common medical and non-medical uses, using National Council on Radiation Protection and Measurement (NCRP) data and other published sources.  Excluding naturally occurring radiation, most of radiation comes from medical use as opposed to non-medical use. In medical use, the bulk of exposure is related to CT and nuclear imaging, especially cardiac. Exposure to nuclear medicine examinations among 65+ individuals is 3 times higher than among 30-44 group, fast growing over time, with higher exposure among females than males. Concern is emerging about rapidly increasing doses among pediatric populations. In non-medical use exposure is minor, coming mainly from cigarette smoking, building materials, and commercial air travel. Results are presented by age and sex, and sensitivity analyses on selected variables are reported. CONCLUSIONS: Given the rapidly growing radiation exposure, our findings might have important implications for the health of the general population. Strategies to monitor and to manage cumulative exposure, especially in medical use in the general population should be developed.