The influence of the characteristics of a sintering atmosphere based on H-2/N-2 gas mixtures, on the sinterability and the resulting mechanical properties of P/M steels containing high oxygen affinity elements, like Cr and Mn, has been studied at 1100 and 1240degreesC. Special attention has been paid, to the control and evolution of critical parameters like oxygen partial pressure and carbon activity, and to their sensitivity in relation to the chemical composition of the initial atmosphere and the sintering temperature. Theoretical thermodynamic calculations referred to the interaction between the atmosphere and the powder compacts based on equilibrium conditions have been considered for various H2/N2 ratios, dew points and small amounts of methane additions. Predictions from these calculations were compared to experimentally obtained results. Microstructural observations from the surface to the core of the specimens and tensile properties according to MPIF standards were carried out. Cr and Mn containing alloyed steels, with 0 and 0.4 wt% C were sintered in selected atmospheres. The carburisation-decarburisation phenomena and the role of carbon during oxide reduction are discussed. The alternative use of a typical endothermic atmosphere was evaluated.