This study has been carried out to evaluate gaseous nitrocarburizing treatment undertaken for pure iron at 570℃ in an atmosphere containing 50% endothermic gas, generated from natural gas, and 50% ammonia. The results obtained from the experiment are as follows ; 1) The microstructure of gaseous nitrocarburized pure iron consists of the compound layer on the surface and the diffusion zone beneath it. The compound layer progresses uniformly into ferrite with a thickness of 20μ obtained after treating for 3 hours. 2) Chemical analysis has shown that the compound layer has a C/N ratio of 0.19 and that the average combined interstitial content of the compound layer is about 30 atomic percent, which is close to the lower limit of the ε-carbonitride phase field in Fe-C-N phase diagram. 3) X-ray diffraction analysis has revealed that the compound layer consists mainly of the c.p.h, phase, ε-Fe₃(C. N) and a small amount of Fe₄N and traces of ferrite are also present in the compound layer. 4) The microhardness of the compound layer is about 600 V.H.N and shows a relatively sharp fall-off at the compound layer/diffusion zome interface. 5) The average actual degree of ammonia dissociation is calculated to be 27% for a gaseous nitrocarburizing treatment carried out at 570℃.