The addn. of Ag to the Al2O3, SiO2 and C-supported Pd catalysts resulted in an increase in their activity and selectivity in the redn. of nitrates and nitrites to N-2, and NH3, but the increase in the catalyst activity was, however, lower than in the case of Cu addn. Formation of solid solns. and intermetallic compds. was evidenced by XRD and ToF-SIMS. The temp.-programmed desorption of CO from the catalyst surfaces revealed a decrease of desorptive peaks with increasing the Ag content in the catalysts. The average size of metal crystallites was lower on Al2O3 support than on the SiO2 one.