Measurements of the hydroxyl nightglow from the Wind Imaging Interferometer (WINDII) satellite-borne experiment and from ground-based photometers are compared and combined in order to characterize the hydroxyl airglow nocturnal behavior at 23 ¿S and the equatorial region. Ground-based observations at Cachoeira Paulista (23 ¿S, 45 ¿W) and at Fortaleza (4 ¿S, 38 ¿W) from 1987 to 1994 and WINDII data from March 1992 to January 1994 are selected, and two periods are studied: the March/April equinox and the December/January solstice. The WINDII results for the equinox/solstice difference and for the nocturnal behavior of the vertically integrated emission rate of the hydroxyl nightglow are found to be in very good agreement with the ground-based observations. The WINDII measurements revealed two general characteristics of the hydroxyl nightglow altitude variation at the latitudes above. The hydroxyl nocturnal variations are predominantly occurring below 90 km, and the vertically integrated emission rate and the peak height of the volume emission rate show an inverse relationship with seasonal, latitudinal, and inter annual effects. The interpretation of these results in terms of atmospheric tides is then discussed. ¿ 1999 American Geophysical Union