The reaction O− + O+ → O(5S or ³S) + O(³P) + KE may be responsible for the recently observed tropical ultraviolet nightglow composed principally of the 1304 and 1356 A lines of atomic oxygen. The O− concentration needed to obtain the observed emission intensity is less than 10−3 of the electron concentration. Emission intensity from this reaction in a steady state is controlled by the production rate of O− which, in turn, is probably controlled by the height-integrated product of atomic oxygen and electron concentration. The quiescent intensity of the UV emission computed for this mechanism is of the order of 100 rayleighs. Some of the consequences of the mechanism are outlined and are compared with the consequences of a radiative recombination mechanism.