The natural radioactivity due to the presence of U-238, Th-232, K-40 and the artificial radioactivity due to Cs-137 in beach sand samples from the Black Sea coast of Kocaeli (Turkey) have been measured by a gamma ray spectroscopy. Activity concentrations of U-238, Th-232, K-40 an Cs-137 varied in the ranges from 4.41 +/- 0.03 to 14.04 +/- 0.04, from 2.62 +/- 0.02 to 16.55 +/- 0.03, from 11.60 +/- 0.25 to 513.32 +/- 3.44 and from 0.56 +/- 0.02 to 5.43 +/- 0.03 Bq kg(-1), respectively. The gamma dose rate in air due to U-238, Th-232 and K-40 in the samples has been estimated to be in the range between 4.10 and 36.80 nGy h(-1). The radium equivalent activity values of all sand samples are calculated and found lower than the world limit of 370 Bq kg(-1). In addition, the calculated values of external hazard indexes varied from 0.0244 to 0.2019, and are lower than unity. (c) 2013 Elsevier Ltd. All rights reserved.