Process for the preparation of an additive-containing anionic clay comprising the steps of (a) preparing a physical mixture of a divalent and a trivalent metal compound, (b) calcining the physical mixture at a temperature in the range 200-800.degree. C. without performing a prior aging or shaping step, thereby forming a product containing at least 5 wt % of a rehydratable compound, and (c) rehydrating the calcined mixture in aqueous suspension containing an additive to form the additive-containing anionic clay.This process provides a simple and cost-effective way of preparing additive-containing anionic clays. The process does neither require aging or reaction steps before calcination, nor does it require precipitation of metal salts or the handling of inhomogeneous slurries.