It is widely accepted in the catalysis literature that the bulk M = O bond of bulk mixed metal oxides controls catalytic activity. In the present study, for the first time, the bulk M = O bond lengths (strengths) and the surface catalytic activity of bulk metal vanadates and molybdates were quantitatively compared to allow examination of this long-standing hypothesis. The bulk M = O bond lengths were obtained from crystallographic studies and also determined by Raman spectroscopy. The surface catalytic activity was determined by CH3OH-temperature programmed surface reaction (TPSR) spectroscopy and steady-state methanol oxidation. The CH3OH-TPSR experiments provided the first-order rate constants for breaking of the C-H bond for the decomposition of the surface CH3O* intermediate to H2CO and the number of catalytic active sites (N-s). The corresponding steady-state methanol oxidation studies provided the equilibrium adsorption constant (K-ads) for breaking the methanol O-H bond and the specific reaction rate (TOF). The findings clearly demonstrate the lack of correlations among k(rds), K-ads, TOF, and the bulk M = O bond length (strength). This finding is not so surprising when one considers that the adsorption step involves breaking the methanol O-H bond and the rate-determining step involves breaking the surface methoxy C-H bond on surface MOx sites, not bulk M = O bond-breaking. (C) 2008 Elsevier Inc. All rights reserved.