This study aims to assess the environmental radioactivity levels of Harran Plain located within the boundaries of the south-eastem province of Sanliurfa, Turkey. In addition to being at the center of Turkey's major irrigation and development project (South Eastern Anatolian Project, GAP), this 1500 km(2) region is famous for its historic attractions. The outdoor gamma dose rates were measured at selected points of the study area using a plastic scintillator. The activity concentrations in the soil samples collected from the study area were determined by gamma spectrometry for the natural radionuclides U-238, Th-232 and K-40 and the fission product Cs-137. The gross alpha and beta activities in the water samples collected from the region was measured using a low-level gamma spectrometry device. A comparison of the measurement results obtained in this study with those of national and world averages are presented in graphical and tabular forms.