Mesospheric wind measurements were made by using the partial reflection technique at a tropical location (Townsville, 19¿ S), and at a mid-latitude location (Adelaide, 35¿ S) in June and November 1978. It is shown that the prevailing winds were typical of expected winter and summer type circulations in June and November, respectively, but there was a large difference in the amplitudes and structure of the diurnal tide between the two sets of observations. In November the tide was stable with a large amplitude and it appeared to 'break' at a height of 86 km. The propagating S1, 1 mode dominated. In June, however, the tide was weak with large day-to-day variability and the evanescent S1,-2 mode was dominant. The semi-diurnal tide amplitudes were relatively small but internal gravity wave amplitudes were significant. Spectral analyses showed that in the 2 to 8 hour period band the wave energy decreased as f-k with k in the range 1--1.5 and it is also shown that the waves were losing energy as a function of height. The inferred energy loss rates were ~0.05 W kg-1 and a turbulent viscosity of about 500 m2 s-1 was estimated near the mesopause at both sites and in both seasons.