Pure VSbO4 phase is not active for propane ammoxidation, unless some segregated alpha-Sb2O4 is present on its surface. Surface vanadium may be necessary to activate propane. For the ternary Sb-V-Nb oxide catalysts: Sb-V-O, Nb-V-O and Sb-Nb-O phases may form. SbNbO4 is inert and forms at the expense of efficient Sb-V-O and V-Nb-O phases. The extent of formation of these phases strongly depends on the preparation method. The Sb precursor determines if V-Sb or Nb-Sb is the preferred interaction. Tuning the interaction of Sb with the other elements affects the catalyst structure and performance. (c) 2005 Elsevier B.V. All rights reserved.