An Fe Boltzmann temperature lidar was used to obtain the first measurements of middle atmosphere temperatures, Fe densities, and polar mesospheric clouds (PMCs) over the North and South Poles during the 1999--2000 summer seasons. The measured temperature structure of the mesopause and lower thermosphere regions in mid-summer at both Poles is consistent with the MSIS90 model. The density profiles of the normal Fe layer between 80--100 km at summer solstice are similar at both the North and South Poles with maximum densities of about 2000 cm-3. Sporadic Fe(Fes) layers were observed at both Poles with peak densities at 106 km altitude. The maximum densities of the Fes layers were 232¿103 cm-3 at North Pole and 6.52¿103 cm-3 at South Pole. PMCs were detected above both Poles. The altitudes of PMCs over the South Pole were consistently 2--3 km higher than those observed over the North Pole. ¿ 2001 American Geophysical Union