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Oxygen adsorption properties of 16 metal oxides were investigated by means of a temperature programmed desorption (TPD) technique. Although oxygen adsorption phenomena were largely different depending on metal oxides, it was possible to classify the oxides as follows: (A) V205, MoOa, Bi203, W03, and 203•2 03 which exhibit no oxygen desorption over the range 10-560 °C; (B) Cr203, Mn02, Fe203, Co304, NiO, and CuO which always give relatively large amounts of oxygen desorption; and (C) Ti02, ZnO, Sn02, A1203, and Si02for which evacuation at high temperature followed by oxygen adsorption at relatively low temperature is required for oxygen desorption to appear over the range 10-400 °C, except the last two oxides. It is noted that group A oxides have layer structures except for Bi2Oa, while group B consists of oxides with cations of d1-d9 electronic structures. Among the oxygen species adsorbed on group C oxides, the 02" ion was directly identified by means of ESR spectroscopy,• and was assigned to specific desorption peaks of respective TPD spectra. The amounts of desorbed oxygen (V^o) for group B and C oxides were only a few percent of the surface coverage, suggesting that the adsorption sites are some sorts of surface defects. There was a fairly good correlation between V560 and the heat of oxide formation per g mol of (-H°), and the amount of adsorbed oxygen tended to decrease with increasing -AH°. These results are discussed in relation to the catalytic properties of the oxides.