[en] Auger electron spectroscopy (AES) studies of the MNN spectra of MoO₃, MoO₂, oxidized Mo foil, and Mo (100) single crystal reveal the splitting of the Auger transition peaks which involve valence electrons. The splitting of these transition peaks is attributed to the altered valence-band density of states which illustrates the existence of two major oxidation states in the specimen. The additional state is caused either through surface oxidation or beam-induced reduction. Based on the M/sub 4,5/N/sub 2,3/V transition peak, the measurement shows the chemical shift to be 5 eV for Mo⁶⁺ and 1 eV for Mo⁴⁺. The reduction of the oxygen Auger peak-to-peak height (APPH) with a simultaneous enhancement of the Mo APPH and sample coloration change in the beam-irradiated area has been observed during electron bombardment of oxide specimens. The observable changes indicate the occurence of beam-induced decomposition and the preferential loss of oxygen from the surface. The electron bombardment mainly causes the reduction of MoO₃ to MoO₂. The efficiency of further reduction to the elemental metal state is low as compared to the reduction process from Mo⁶⁺ to Mo⁴⁺. Comparison of predicted Auger intensities, based on the contribution to the total Auger intensity from each atomic plane, with the experimental observations confirms the formation of a Mo⁴⁺-rich surface layer on a beam-irradiated specimen