Abstract The environmental impact of uranium mill tailings can be expressed in collective dose commitment and corresponding detriment per MWe*y energy produced by the uranium which corresponds to the amount of waste of interest. The methods of dose commitment calculations are discussed and it is suggested for the purpose of estimation of the detriment to limit the commitment to 10,000 years. The external radiation from the tailings is easily reduced by covering but in case of a future settlement on the tailings the collective dose commitment will be some hundreds to thousands of manrad/MWe*y depending on the quality of the uranium ore. The dispersion of dust from uncovered tailings is mainly a local problem and the collective dose commitment for critical tissues in the lung will be less than a manrad/MWe*y. In the long run the cover may be lost and the resultant collective dose commitment for the critical tissues in the lung will be a few tens of manrad/MWe*y depending on the quality of the tailings. The effects of global dispersion of the material in the tailings are also discussed.