Large quasi-periodic fluctuations are observed simultaneously in the rotational temperature of the nightglow emission from both O2(1&Sgr;g) and OH. The fluctuation amplitude usually is several times larger in the former and the O2(1&Sgr;g) fluctuations often lead those of OH in phase. This behavior is consistent with that expected for internal gravity waves propagating upward over the ~10 km vertical separation between the two emission layers. The most prominent periods are 1-2 hours and the full range of oscillation in temperature at 95 km sometimes approaches 100 ¿K.