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Exposure to alpha, beta or gamma radiations from natural sources, which is varies by location and altitude, affect the living organism. The main sources are earth crust (83%) and cosmic (17), with annual exposure 2.0 mSv and 0.4 mSv, respectively. The objective of this study is to identify the radionuclide concentration in certain cities (Riyadh , Hagl and Khafji), of Saudi Arabia. The radionuclide were identified using gamma spectroscopy equipped with a high-purity germanium (HPGe) detector during twelve months. The results illustrate the observation of Be-7 (T1/2= 53.3 days), K-40 (T1/2= 1.251×109 years) , Cs-137 (T1/2= 30.17 years) and Ra-226 (T1/2= 1600 years) with average activity concentration in surface air samples (mBq/m3) of 11.8±0.7, 1. 9±0.1, 0.01±0.0 and 0.24 ±0.03 at the same order in Riyadh city which is located in the central of Saudi Arabia. In addition, comparable concentrations were measured in Hagl and Khafji cities which are located in both north corners of Saudi Arabia. Various concentration of Be-7 were noticed during certain time in a year, depending on the variation of the environmental conditions (climate) and the geographical location. This can be attributed to fact that B-7 is produced in upper atmosphere and transported to troposphere.
