Nickel aluminide compounds were synthesized by the thermal explosion mode of the self-propagating high temperature synthesis (SHS). The effects of green density and heating rate on the combustion characteristics and the microstructure of the products were studied. It was found that the combustion can not be ignited with heating rates lower than 5 K min(-1). In this case, the formation of NiAl can be achieved by classic reactive sintering. At heating rates higher than 5 K min(-1), a precombustion stage exists for compacted samples allowing the ignition of the reaction at low temperature. Combustion temperature were found to be higher than thermodynamic predictions in argon and, moreover in air, because of the formation of aluminium oxide which triggers the NiAl synthesis reaction.