Gamma rays, the most energetic photons within the any other wave in the electromagnetic spectrum, pose enough energy to form charged particles and adversely affect human health. Provided that the external exposure of human beings to natural environmental gamma radiation normally exceeds that from all man-made sources combined, envi-ronmental gamma dose rate and corresponding annual effective dose were determined in the cities of Ardabil and Sar Ein. Outdoor environmental gamma dose rates were measured using an Ion Chamber Survey Meter in 100 selected loca-tions (one in city center and the remaining in cardinal and ordinal directions) in Ardabil and Sar Ein. Measurements of gamma radiation dose rate were performed at 20 and 100 cm above the ground for a period of one hour. Average outdoor environmental gamma dose rate were determined as 265 and 219 for Ardabil and Sar Ein, respectively. The annual affective dose for Ardabil and Sar Ein residents were estimated to be 1.45 and 1.39 mSv, respectively. Calculated annual effective dose of 1.49 and 1.35 are appreciably higher than the population weighted average exposure to environmental gamma radiation worldwide and that analysis of soil content to different radionuclide is suggested
