Today, cordierite plays a very important role in the reduction of noxious substances emitted from internal combustion engines. Honeycomb structures with parallel channels offer a good solution as supports for catalysts at an acceptable counterpressure. Porous ceramic materials permit an efficient mechanical filtration of carbonaceous particles contained in the exhaust gases of diesel engines, which are forced to flow through the walls. Interest in these components is increasing due to their potential effectiveness; it is therefore important to study the problems sometimes encountered during actual applications. This research considers the interaction between some oxides encountered in practical use and the material itself in order to understand the behaviour of cordierite as a basis for better utilisation; some observations and comments are reported.