Upper atmospheric airglow emissions in the mesopause region, OI557.7 nm, NaD at 589.3 nm and OH(9,4) band at 774.6 nm have been observed since 1977 at Cachoeira Paulista (22.7¿S, 45.0¿W), Brazil. The seasonal dependence of the intensity variations of these emissions was studied using the data from a total of 560 nights, during the period June 1977 to November 1986. Strong semiannual variations in the NaD and OI557.7 nm emissions were observed with maxima at the equinoxes, in contrast to the OH(9,4) emission, which showed a much smaller seasonal variation. Hydrogen and ozone concentrations at around 87-89 km were calculated using the observed NaD and OH(9,4) band intensities and the sodium concentration observed by lidar at a nearby station. The obtained seasonal variations of the two species, opposite in phase with each other, are in good agreement with current atmospheric dynamics models, which show a seasonal variation of the vertical transport of atomic oxygen and hydrogen. ¿ American Geophysical Union 1992