Epidemiological studies of occupational, medical, and environmental exposures have provided important information on lung cancer risk and how those risks might depend on the type of exposure, dose rate, and other potential modifying factors such as sex and age of the exposed. Analyses of data from underground miner cohorts and residential case-control studies provide convincing evidence that radon is a leading cause of lung cancer. For low-LET radiation, risk models derived from results from the Lifespan Study of Japanese atomic bomb survivors suggest that for acute exposures, lifetime attributable risks for lung cancer are greater than for other specific cancer sites and are substantially larger for females than males. However, for protracted and fractionated exposures other than from radon, results from epidemiological studies are seemingly often contradictory.This report includes summaries of oral presentations during a symposium on radiogenic lung cancer risk given by a panel of experts on October 5 during the Radiation Research Society’s 67th annual meeting. This session included presentations on: 1) the largest pooled study of male uranium miners (PUMA) exposed to radon; 2) the most recent analysis of the Canadian Fluoroscopy cohort featuring state-of-the-art dosimetry for radiation exposures associated with frequent medical diagnostic procedures; 3) an update from the Million Person Study on risks from fractionated occupational exposures, and 4) studies of second primary malignancies – including lung cancer – in patients who had been treated for thyroid cancer.