(NH4)(6)TeMo6O24.nH(2)O and (NH4)(4)TeMo6O22.H2O telluromolybdates have been prepared by using a solution reaction and a hydrothermal synthesis, respectively. They have been decomposed in the presence of air or N-2 in order to achieve mixed metal oxides to be used as catalysts in the selective oxidation of propene. Both the characterisation and the catalytic results suggest important differences in the catalysts depending on the starting material and the calcination conditions. In this way, active and selective catalysts for the oxidation of propene to acrolein have been obtained by using (NH4)(4)TeMo6O22.2H(2)O (prepared by hydrothermal synthesis) as starting material. (C) 2002 Elsevier Science B.V All rights reserved.