This dissertation is devoted to the use of NAA to be applied for the determination of thernqualitative and quantitative elemental analysis of selected samples. It involves the use ofrnthe knowledge of nuclear reaction particularly (n; rn) reaction and implement its practicalrnapplications to determine element types and their concentrations in the sample. In lab,rna total of Five di erent biological and geological samples were studied, four samples werernstudied for their qualitative and quantitative elemental analysis and one soil sample wasrnstudied for its natural radioactivity. Long lived and short lived radionuclides spectra werernmeasured using HPGe gamma detector. Using known values of gamma-ray energies ema-rnnating from calibrating point gamma sources, an energy calibration curve and full energyrnpeak e ciency curve were determined and plotted. The best t line matched the datarnwith a least squares t, R2, of approximately equal to 1.rnA gamma spectrum is created by taking measurements of emitted gamma-rays from dif-rnferent radio nuclei which emit many gammas of di ering energies. Special softwares,rnacquisition software MAESTRO and analysis software WINSPAN, installed in comput-rners identify an unknown radioisotope by measuring features on the gamma spectrum andrncomparing them to known spectra, and calculate the concentrations of the elements whichrngives out the gamma radiation. The peaks of di erent energies in the spectrum were testedrnanalytically using the half lives of radionuclides whether the assignment of an element torneach peak by the analysis software is correct. The analysis methodologies were validatedrnby analyzing the IAEA-multi elemental standard having the same matrices as the sample.rnThe irradiation facility used was the Nigeria Research Reactor-1 (NIRR-1) at the Centerrnfor Energy Research and Training (CERT), Ahmadu Bello University, Zaria, Nigeria. Arnhigh resolution gamma-ray spectrometer comprising of HPGe detector coupled with asso-rnciated electronics and basic spectroscopy softwares were employed in the analysis. Fromrnthe analysis of samples of biological and geological origin, di erent concentrations of el-rnements were obtained and an e ort is made to explain the function of the elements forrnhuman or animals. In this dissertation a mineral soil was measured for its radioactivityrnand the concentration of radioactive materials were analysed and the level of radiationrnhazard due to the soil is calculated