Abstract: The production of SiC whiskers and of mats thereof on a substrate by treatment, at 1250.degree. to 1500.degree. C., of a gaseous mixture including hydrogen and sources of Si and C atoms which are in the form of at least one oxygen-free compound, in the presence of a metal type catalyst, by a semi-continuous or periodic process, is characterized in that, during the growth period, an Al-Fe catalyst is introduced into the gas phase in the reaction zone, by means of carbon reduction of aluminosilicate ceramics, which comprise at least 73 weight % of Al.sub.2 O.sub.3 and 0.3 to 3.0 weight % of iron oxides and the substrate is a carbonized rayon fiber based carbon fabric which has been pre-treated, prior to carbonization, with a solution of borax and a solution of diammonium phosphate until the quantities of boron and phosphorus in the fabric do not amount to more than 4 and 2 weight %, respectively.