The structure/composition and catalytic behavior in propane ammoxidation to acrylonitrile of Sb-V-oxides prepared by a novel precipitation-deposition method is reported and the nature of the active components in these catalysts is discussed. Results suggest that the active phase for the selective synthesis of acrylonitrile from propane is a trirutile-like V-antimonate with Sb5+-oxide supported on it. Vanadium plays a catalytic role in the selective activation of propane and reoxidation of antimony, but when present in large amounts on the surface catalyzes the unselective NH3 --> N-2 conversion with a lowering in acrylonitrile selectivity. alpha-Sb2O4 is instead a side phase, with a marginal or negligible role in the catalytic behavior.