Abstract: Process for the production of moulded bodies of materials based on silicon nitride, where the powder mix prepared by way of initial material contains silicon nitride (Si.sub.3 N.sub.4), a high proportion, preferably 40-85 percent by weight, of silicon (Si) and a sintering aid. With conventional sintering the above powder mix is advantageously prepared by grinding of an Si-powder dispersed in an Si.sub.3 N.sub.4 powder the grain size of which is considerably lower than that of the Si-powder. The process covers in the main the production of a body moulded from this powder mix by known moulding methods, nitriding of the Si-content to Si.sub.3 N.sub.4 and sintering of the moulded body to a final required density.