Results are presented of month by month measurements of the mean wind and intensity and momentum fluxes of internal gravity waves (IGWs) with the Middle and Upper atmosphere radar (MU radar) at the altitudes 65--80 km at Shigaraki, Japan (35 ¿N, 136 ¿E) in 1986--1997. The mean zonal wind is eastward in winter and westward in summer, but the amplitude of these annual variations is different in different years, having a minimum in 1992--1994. The mean meridional wind shows substantial quasi-bi-annual variations. IGW intensities and momentum fluxes had a maximum in 1991--1994. Some possible reasons for such interannual changes are discussed. ¿ 1999 American Geophysical Union