Using Rayleigh lidar and Mesosphere-Stratosphere-Troposphere radar at Davis Antarctica (68.6°S) during the 2005–2006 austral summer, we obtained the first Southern Hemisphere common-volume measurements of Polar Mesospheric Clouds (PMC) and Polar Mesosphere Summer Echoes (PMSE). PMC were observed with 6% probability during 349 hours of lidar observations. PMSE were simultaneously observed during 70% of the PMC events. The mean centroid altitudes of simultaneous PMC and PMSE were 83.97 ± 0.10 km and 85.31 ± 0.14 km, respectively. The altitude difference (∼1.3 km) is comparable to earlier boreal common-volume measurements. Both phenomena show clear diurnal variations in altitude and occurrence. PMC had a unimodal local time occurrence distribution which peaked 4–6 hours after solar midnight. PMSE were most prevalent at this time, but had a secondary occurrence peak ∼6 hours after solar noon when PMC were absent. We explain the altitude-time distributions of PMC and PMSE in terms of the thermal structure of the mesopause region determined using measurements from the Aura satellite.