We present mesospheric wind data from MU radar at Shigaraki (34.9 ¿N, 136.1 ¿E), Japan, that exhibit a wave motion with a vertical wavelength of 6 km. An analysis of the horizontal and vertical components of the observed wind velocity shows that the wave motion is due to an internal inertia-gravity wave. It behaves like a stationary wave, similar to lee waves. With the estimated wave parameters, we can derive the mean mesospheric temperature modes. The temperature is shown to be quite consistent with the mean state of the atmosphere. It is further shown that a scattering echo layer observed simultaneously was closely connected with the vertical propagation of the gravity waves. ¿ American Geophysical Union 1987