A series of monometallic (In, Co) and bimetallic (In/Co and Co/In) catalysts supported on ferrierite type zeolite were tested in the selective catalytic reduction of nitric oxide, in the presence of methane and excess of oxygen. All the catalysts were prepared by contact-induced ion exchange. A strong synergistic effect was observed for the catalysts containing both indium and cobalt, in comparison with the monometallic samples. For these bimetallic catalysts, a very high selectivity to nitrogen and rather efficient fuel economy were observed under the standard reaction conditions (NO = 1000 ppm, CH4 = 2000 ppm, O-2 = 4%, H2O = 2500 ppm). Moreover, the In/Co-ferrierite catalyst displays significant stability under a prolonged test (similar to 200 h) in the presence of 2.5% of steam: the activity dropped rather moderately but was completely restored if steam supply was cut off, while the selectivity of the reaction was not affected in the whole temperature range scanned (300-500 degrees C). The study suggests that a redox-type promotional effect of Co species on NO oxidation may be responsible of the strong synergistic effect detected in bimetallic In-Co formulations. (c) 2006 Elsevier B.V. All rights reserved.