Pre-operational survey at Kalpakkam coast, indicated elevated gamma background radiation levels in the range of 100-4000nGyh - 1 over the large tracts of the coastal sands due to the presence of pockets of monazite mineral in beach sands. In view of the prevalence of monazite, a systematic gamma spectrometric study of distribution of natural radionuclides in soil and beach sand samples collected from the terrestrial and coastal environment of Kalpakkam was performed and concentrations of primordial radionuclides such as 2 3 8 U, 2 3 2 Th and 4 0 K and anthropogenic radionuclide 1 3 7 Cs were determined. The concentrations of 2 3 8 U, 2 3 2 Th and 4 0 K in soil samples were 5-71, 15-776 and 200-854Bqkg - 1 dry, respectively. In beach sand samples, 2 3 8 U, 2 3 2 Th and 4 0 K contents varied in the range of 36-258, 352-3872 and 324-405Bqkg - 1 dry, respectively. The total absorbed gamma dose rate in air due to the presence of 2 3 8 U, 2 3 2 Th and 4 0 K in Kalpakkam soil samples varied between 24 and 556nGyh - 1 with a mean of 103nGyh - 1 . The contribution to the total absorbed gamma dose rate in air in the decreasing order was due to the presence of 2 3 2 Th (76.4%), followed by 4 0 K (16.9%) and 2 3 8 U (6.7%) in Kalpakkam soils. However, in beach areas of Kalpakkam, the presence of 2 3 2 Th in beach sand contributed maximum (94.0%) to the total absorbed gamma dose rate in air followed by 2 3 8 U (4.7%) and minimum contribution was by 4 0 K (1.3%). 1 3 7 Cs in Kalpakkam soils ranged from =<1.0 to 2.8Bqkg - 1 dry, which was 1-3 order of magnitude less than the concentration of primordial radionuclides in soil.