Background:Measurement of environmental exposure is very important from different points of view especially for human health. In Iran, it is measured in some cities especially in high background areas such as Ramsar, but so far there is not any measurement in Isfahan.Material/Methods:Measurements were performed using CaSO4: Dy TLDs. The locations under investigations were 52 health centers distributed all around Isfahan city. Each TLD badge was put in a special plastic bag and left over the roofs of the selected health center for a month. The procedure was repeated for all 12 months of the year 1379 (21st March 2000 to 20th March 2001).Results:The maximum and the minimum of obtained results for dose equivalent in different months and locations were 15.9i10–2 and 6.5i10–2 mSv. Obtained maximum and minimum of the means between all the locations were 10.5i10–2 and 8.6i102 mSv for the whole year. Monthly mean and SD for Isfahan city for the whole year were 9.7i10–2 and 1.5i10–2 respectively therefore mean annual dose equivalent in Isfahan city is 1.16I0.18 mSv. The results do not show any high background radiation area.Conclusions:From the total of 624 measurements at 52 sites of Isfahan, obtained annual outdoor X and gamma ray dose equivalent for a person living in isfahan is 1.16I0.18 mSv. This figure is about 48.3% of the world average total radiation background reported by UNSCEAR.

Keywords: Background Radiation, Cities, Environmental Exposure, Gamma Rays, Iran, Periodicity, Radiation Monitoring, X-Rays