Twenty Concrete Blocks each from one of the selected Local Government Areas of Katsina state were investigated. The activity concentration of 40K radionuclide in each of the block sample was measured by means of Gamma-Ray Spectroscopy using Sodium Iodide Thallium [NaI (Tl)] detector and was found to range from 46.11±8.55 to 826.59±4.82Bq/kg with the calculated mean concentration value of 229.98±5.22Bq/kg, which is less than the International permissible values of activity concentration of 4810Bq/kg

Keywords : Gamma-Ray Spectroscopy, radium equivalent, absorbed dose rate, annual effective dose equivalent.