Due to increased global demand for clay, the present work involves the use of gamma ray spectrometry for the measurement of concentrations of natural radionuclides in clay samples. The activity concentration of 226Ra, 232Th and 40K were determined in 32 clay samples collected from Tiruvannamalai district, Tamilnadu by using NaI(TI) detector. The activity concentration of these radio nuclides is compared with world average values. The radiation exposure risk due to natural radionuclides, as a result of the use of clay as raw materials in construction, the radiation hazard indices such as radium equivalent activity (Ra<inf>eq</inf>), criteria formula (CF) and the external hazard index (H<inf>ex</inf>) due to internal exposure to radio nuclides distributed in clay samples have been computed. From the analysis, clay samples could be used as a raw material for brick industry and clay data are useful to those dealing with clay applications. © 2017 Elsevier B.V., All rights reserved.