Several workers have concluded that analysis of the OH infrared emission from the upper mesosphere and lower thermosphere requires population of OH (v=5, 6) by the reaction O+HO2 → OH(v≤6)+O2. It has been stated previously that this may be unlikely if the reaction proceeds by O atom transfer rather than H atom transfer. We show here that recent laboratory evidence argues convincingly that the mechanism of this reaction involves O atom transfer after formation of an HO3 complex and that little or no population of highly vibrational levels (v≥4) of OH are expected, although nonnegligible population of lower level seems plausible. On this basis it appears that this reaction should not be contributing substantially to emission from OH(v=5, 6). The reverse reaction, OH(v≥6)+O2 → HO2+O, which has been suggested to be a potential sink for OH(v≥6), is considered and expected to be slow unless an HO3 complex is formed, in which case, multiple quantum deactivation of OH is also a likely process. Recent experimental evidence suggesting that OH(v=4, 5) may be populated by the H+O3 → OH+O2 reaction is discussed, although no firm conclusions about its importance can be reached. ¿ American Geophysical Union 1988