Studies of the NO decomposition reaction on Pd/gamma-Al2O3, Mo/gamma-Al2O3 and PdMo/gamma-Al2O3 catalysts were made. The catalytic tests revealed that the binary catalyst has different behavior for the NO decomposition, being the principal differences a longer steady state activity and an increase of oxygen evolution at elevated temperatures. Characterization by TPR, hydrogen chemisorption and FT-IR of CO indicated that palladium physicochemical properties are altered by an effective interaction with molybdenum. The results would suggest a decoration effect of Mo over Pd particle. This interaction appears to be responsible for the observed modification in NO activity and selectivity. (C) 2003 Elsevier Science B.V. All fights reserved.