Abstract
The response features for sodium iodide detector for a monoenergetic gamma-ray source are calculated because of the importance of this type of detector in industry and research. The response features calculated are: full energy peak, single scattered escape, single escape peak, double scattered escape, double escape peak, besides single scatter, double scatter and triple scatter continua. These features are compared for different sizes and geometric efficiencies of the detector. The Monte Carlo simulation provides the weighting factors of the previously mentioned eight features of the response for the Nal detector that are necessary for response function generation for that type of detectors.