Rayleigh lidar measurements of the stratosphere and mesosphere have been made on an ongoing basis over a three-year period at Poker Flat, Alaska (65¿ N, 147¿ W). These observations have yielded 27 nightly measurements of the middle atmosphere temperature profile (~40--80 km). These nighttime measurements are distributed between August and April. Mesospheric inversion layers have been observed on five occasions. The average altitude of the inversion layer peak is 60 km, with average amplitude of 18 K. The temperature gradients on the topside of the inversion layers approach the adiabatic lapse rate. The inversion layers do not exhibit the apparent downward phase velocities that are commonly observed at lower latitudes. Furthermore, the inversion layers appear significantly less frequently than at lower latitudes. The observations are discussed in terms of current models and observations at other sites. ¿ 2001 American Geophysical Union