We describe a model for the response of atomic oxygen and hydroxyl airglow to a gravity wave. The airglow models uses a realistic atmospheric-gravity-wave model, describing the wave velocity and pressure fluctuations in the presence of a nonisothermal background temperature profile and background winds. The gravity-wave model is coupled to the OH photochemical model of Makhlouf et al. <1995> and to a simple chemical model for the 557.7 nm airglow as described below. It is shown that the chemistry of the 557.7 nm airglow does not affect the phase of the Krassovsky &eegr;, due to the short chemical lifetime of the O(1S) and the O2(c1∑u-) precursor states, whereas for the OH airglow the chemistry and dynamics couple for wave periods of 10--25 min, and chemistry does affect the phase of &eegr;. The effect of standing waves and traveling waves on the phase of &eegr; is shown to be different, and this behavior can be used to differentiate between freely propagating waves and ducted waves. These effects are illustrated by applying the model to examples of Airborne Lidar and Observations of Hawaiian Airglow (ALOHA-93) campaign data. A combination of model prediction and ground-based measurements from the ALOHA-93 campaign are used to estimate the vertical eddy diffusivity Dzz due to nonlinear gravity waves following the formulation of Weinstock <1976>. The estimated values of Dzz vary between 1.0¿102 and 5.0¿103 m2/s, which is in the range of measured and inferred values. ¿ 1998 American Geophysical Union