Effective atomic numbers for total gamma-interaction\((\bar Z_{tot} )\) are estimated in the energy region (145÷1330) keV in Monel metal and tungsten steel. They are found to be independent of energy in case of Monel metal but dependent on energy in case of tungsten steel. The incoherent-scattering cross-sections are extracted and compared with the theoretical cross-sections of an equivalent element and also with the cross-sections obtained by a sum rule using the theoretical data. Good agreement is observed in all the cases within the experimental errors confirming the constancy of effective atomic number for incoherent scattering\((\bar Z_{inc} )\) and also the applicability of the Hine’s expression for\(\bar Z_{inc} \).