The present invention relates to a process for the preparation of doped pentasil-type zeolite, which process comprises the steps of:

a) preparing an aqueous precursor mixture from a silicon source, an aluminium source, and doped non-zeolitic seeds; and

b) thermally treating the precursor mixture to form a doped pentasil-type zeolite.

The term "non-zeolitic seeds" includes seeds made from materials selected from the group consisting of (i) X-ray amorphous materials, (ii) milled crystalline materials, such as milled zeolites, that have a relative crystallinity of not more than 75%, and (iii) crystalline materials other than zeolites, such as clays (e,g, bentonite and kaolin) and (low) crystalline aluminas.