Energy spectra resulting from the scattering of gamma rays under various conditions were calculated by a Monte Carlo method. As a result of systematic studies on the low energy components of the spectra, it was found that they were not affected very much by source energy or scatterer geometry but were affected by the atomic number of the scatterer. These properties could be explained successfully by a relatively simple theory including the continuous slowing down approximation. A formula expressing the relationship between the position of the peak appearing in the low energy region of the spectrum and the atomic number of the scatterer was derived from the above calculations and the theory.