The reburning process with natural gas is an effective technique which can be applied in existing coal combustors in order to reduce the NO(x) emissions. The influence of the reburning temperature (1200-1500-degrees-C) and the oxygen concentration coming from the primary combustion zone (0-5%) have been studied. Experimental results of NO, HCN, NH3, CO, CO2, and CH4 concentrations in the exit gas have been determined. The influence of the natural gas decomposition on these results has been analyzed. The experimental trends obtained have been compared with those calculated with the model of Kilpinen et al. (1992).