Rn exposures to USA U miners under present conditions average .apprx. 1.3 WLM[working level mo.]/yr .apprxeq. 60 WLM/full working lifetime. This was intermediate between the lowest exposures for which excess lung cancers were reported among USA miners (120-240 WLM) and the average environmental Rn exposures (16 WLM), so models based on these 2 situations were used to estimate expected effects on present U miners. In model A, the loss of life expectancy was 45 days, the SMR (standardized mortality ratio) for lung cancer was 1.10, and the SMR for all causes between ages 18-65 yr was 1.013. In model B these were 10 days, 1.03 and 1.002, respectively. Rn exposures to miners were similar to those to millions of Americans from environmental exposure, and miner health risks were comparable to those of other radiation workers. Their lung cancer risk from Rn was 7-50 times less than their job-related accident mortality risk and represented 0.7-4% of their total risk in mining. Miners suffered from many diseases with SMR larger than that for Rn-induced lung cancer, and there were many other occupations and industries with higher SMR for lung cancer than that from Rn exposure to miners.