The National Institute for Occupational Safety and Health (NIOSH) has recently updated the vital status of the U.S. cohort of U miners through the end of 1982. This represents 69 additional lung cancer deaths since the last published follow-up through 1977. This more recent data was used to generate quantitative risk estimates of lung cancer after exposure to Rn daughters. Relative risks were estimated through use of the Cox proportional hazards model with an internal referent group. Results indicated that the exposure-response relationship was a slightly convex curve, predicting excess relative risks between 0.9 and 1.4 per 100 working level months (WLM) in the lower cumulative exposure range. Other findings of interest include a significant exposure-rate effect with low exposure rates more harmful per unit of cumulative exposure (WLM). Two temporal effects which modify relative risk estimates were also found. Relative risk increased with age at initial exposure to underground U mining. However, relative risk of lung cancer fell dramatically in the years following cessation of exposure.