Objective: This review presents epidemiological studies on workers exposed to low doses of ionizing radiation. Method: The review includes the following populations: radiologists and radiology technicians, miners, flight crew, and nuclear workers. Studies were selected from the National Library of Medicine’s medical reference database (MEDLINE). All cohort studies were included without date restrictions. Results: Radiologists and radiology technicians were among the first to be occupationally exposed to ionizing radiation. Excess rates of leukemia, lung cancer, and skin cancer were observed among practitioners who worked before World War II. For more recent years, studies still lack sufficient follow-up to draw conclusions. Studies conducted among underground miners have shown a dose-response relationship between radon exposure and lung cancer. This relationship diminishes with the time elapsed since exposure and with age at exposure. An increase in the effect with dose fractionation is also suspected. Excesses of malignant melanomas and breast cancers have been observed among flight crew. This population is exposed to cosmic radiation, jet lag, and has irregular work schedules. Factors related to lifestyle (sun exposure) or reproductive history may partly explain these excesses, but they appear insufficient. Finally, among nuclear workers, the diseases for which a dose-response relationship is most frequently observed are leukemias other than chronic lymphocytic leukemia and multiple myeloma, with a relative excess risk of approximately 2 per Sievert for the former and 4 for the latter. Lung cancers are also implicated, but potential confounding factors are significant: internal radiation exposure and other occupational exposures. Conclusion: This review highlights significant findings in the epidemiology of occupational exposure to ionizing radiation. It underscores the need for further studies to confirm the observed dose-response relationships and to understand certain excesses. It also highlights the need for systematic epidemiological surveillance and post-occupational follow-up of all affected personnel.