Inhalation of tobacco smoke is ranked second to food as a source of210Pb and210Po exposure to man. Assay of210Pb and210Po in commercially available tobacco collected from many countries have been carried out to assess the potential risk from210Po present in tobacco.The range of210Po contained in the tobacco grands varied from 10.08 to 15.0 mBq/tob or 13.0 to 20.1 mBq/g and the mean was 11.6 mBq/tob or 15.4 mBq/g. During the International Standard Smoking process about 50% of210Po present in tobaccos was transferred into the smoke and the other 50% remained in the ash and butt. About 10% of the total210Po of tobacco was inhaled by smoke through mainstream smoke. One pack-a-day smoker inhaled 24 mBq of210Po per day through smoking and the annual inhalation was 8.8 Bq. The risk of mortality from lung cancer caused by210Po in tobaccos was 18 per million persons for the above model.