Measurement of the activity concentrations of terrestrial and anthropogenic radionuclides in one hundred fifteen soil samples collected from various locations in Samsun city was taken using a gamma-ray spectrometer with a NaI (Tl) detector. The average activity concentrations of terrestrial radionuclides Ra-226, Th-232, and K-40 were measured as 38.1 +/- 1.4, 39.3 +/- 0.8, and 375.3 +/- 10.2 Bq kg(-1), respectively. The average activity concentration of anthropogenic radionuclide Cs-137 measured in some soil samples was found as 12.1 +/- 0.7 Bq kg(-1). Radon concentrations in soil and in air were estimated using results of the measurement of activity concentrations of Ra-226. The average concentrations of radon in soil and air were found as 32 kBq m(-3) and 101 Bq m(-3), respectively. The absorbed gamma dose rate in outdoor air due to terrestrial radionuclides in soil samples varied from 28 to 95 nGy h(-1) with an average of 57 nGy h(-1). The annual effective dose rates caused from external and inhalation exposure were estimated as 70 and 958 mu Sv y(-1), respectively.