Pd-Mo/gamma-Al2O3 catalysts were prepared by wet impregnation using organometallic precursors. The performance of these catalysts in the selective catalytic reduction of NO by methane (denoted NO-CH4) was compared with corresponding palladium- and molybdenum-supported catalysts prepared by the same method. Characterization by TPR, hydrogen chemisorption and FTIR of CO and NO showed evidence of palladium-molybdenum interaction. The experimental results indicated an encapsulation effect of partially reduced Mo species over Pd particle. The catalytic tests revealed that the binary catalysts have different behaviors for the studied reaction. The activity for NO-CH4 reaction is higher for the binary samples in the temperature range 200-500 degreesC. On the other hand, a decrease in the activity (at 500 degreesC) was observed over the Pd-Mo/Al2O3 samples after 2 h under reaction conditions, being similar to the activity displayed by Pd/Al2O3. This is thought to be associated with a poisoning of MoOx sites by the oxygen formed during the dissociation of NO. The oxygen taken up by the MoOx species does not seem to be removed by methane. Higher initial activity on bimetallic catalysts is attributed to the greater number of active sites and a synergetic effect between Pd and Mo. (C) 2003 Elsevier Science B.V. All rights reserved.