The natural background radiation dose level in Taiwan was reassessed by using the measured data and the newly published dose conversion factors. The indoor gamma dose rate in Taiwanese houses in 72 nSvh - 1 , which is high as compared with other countries, but the indoor radon level is much lower than most other countries. The annual effective dose for adults in Taiwan is 1.56 mSv, including 0.25 mSv from cosmic rays, 0.58 mSv from terrestrial external radiation, 0.28 mSv from terrestrial internal radiation, and 0.36 mSv from inhalation of 2 2 2 Rn. The other minor components, such as cosmogenic radionuclides, inhalation of 2 2 0 Rn, and ingestion of 2 2 2 Rn, are estimated to be at the same level as the world average. The natural radiation dose level is only about 23 of the global average quoted in the UNSCEAR 1993 Report.