A catalyst, or a precursor thereto, comprises, as the active material or as a support therefor, a ceramic foam having a network of irregular passages extending therethrough, said passages having an average minimum dimension in the range 20 to 300 .mu.m, said foam having a total porosity in the range 40 to 85% and an apparent density of at least 0.7 g.cm.sup.-3. The foam may be made by forming a negative replica of an open cell plastics foam by impregnation of the latter with a dispersion of the ceramic material, followed by drying and calcining the impregnated foam to remove the plastics material and to cause the ceramic material to sinter.For a steam reforming catalyst the ceramic may be alpha alumina and the active material nickel and/or cobalt.