A catalyst for the selective reduction of nitrous oxide with ammonia contains, in addition to titanium oxide as component (A), at least one oxide of W, Si, B, Al, P, Zr, Ba, Y, La, Ce and at least one oxide of Y, Nb, Mo, Fe, Cu as component (B), whereby the atomic ratio between the elements of components (A) and (B) amounts to 1:0.001 up to 1. The catalyst can be obtained by kneading reactive titanium oxide with a high specific surface of predominantly anatase with the substances of component (B) or their preliminary stages, adding processing agents, winding up with a homogeneous kneaded mass, extruding the latter, drying the extrudate and calcining in air at 300.degree.-800.degree. C.