In December 1989 a Na lidar was installed at the Amundsen-Scott South Pole Station and was used to measure aerosol, stratospheric temperature and mesospheric Na profiles through October 1990. The mesospheric Na data are used to characterize the gravity wave field in the mesopause region. These first lidar observations of Na layer dynamics at the South Pole show strong wave activity during the Antarctic winter. Data for 25 June and 19 August 1990 UT are presented here. The total wave induced variances in atmospheric density are respectively 29 and 35 (%)2. The Na layer centroid height is very low during both observation periods. On 25 June a strong 12 h oscillation is observed in the bottomside of the Na layer which extends to altitudes as low as 74 km. The vertical displacement and temperature amplitudes associated with the 12 h oscillation are respectively 1.9 km and 19 K. The characteristics of the 12 h wave are similar to the pseudotide observed at Syalbard by Walterscheid et al. [1986>. ¿American Geophysical Union 1992