Mo-V-Te and Mo-V-Te-Nb mixed oxide catalysts, with different Mo/Te, Mo/V and Mo/Nb atomic ratios have been prepared from aqueous solutions of the corresponding salts, dried at 120 degreesC and heat-treated at 600 degreesC for 2 h in a N-2 stream. They have been characterised by several physico-chemical techniques (AAS, S-BET, XRD, DRS-UV-Vis) and tested in the selective oxidation of both propane and propene. Low specific surface areas have been obtained in all cases. However, both the nature of crystalline phases and the catalytic performance depend strongly on the catalyst composition. All the catalysts were active in propene oxidation but only some of the Mo-V-Te-Nb-O catalysts were also active and selective in the oxidation of propane to acrylic acid. The nature of active and selective Mo-V-Te-Nb-O crystalline phases is also discussed. (C) 2004 Elsevier B.V. All rights reserved.