A preliminary study of wood exposed to outdoor weathering as well as to ultraviolet irradiation showed that electron spectroscopy for chemical analysis provides valuable information and insight into weathering and photo-oxidation. The increase in signal intensities of carbonoxygen bonds and oxygen-carbon-oxygen bonds (or unsaturated carbon-oxygen bond) and oxygen-to-carbon ratio, and the decrease in carbon-carbon and carbon-hydrogen bonds of weathered and ultraviolet-irradiated wood surfaces suggested superficial oxidation. Only a slow oxidation was observed at 100 microns under the exposed wood surfaces. The oxygen-tocarbon ratio data revealed that weathered wood surface was rich in cellulose, poor in lignin. The degradation products leached from weathered wood accounted for the discrepancy between the electron spectroscopy for chemical analysis line shapes of ultraviolet-irradiated and weathered wood surfaces. -- AATA