To investigate long-term variabilities of radar echo intensities from the mesosphere, we have analyzed a 10-year data set obtained with the middle and upper atmosphere (MU) radar at Shigaraki, Japan (34¿ 51', N, 136¿ 6' E) during the period from 1986 to 1995. Two types of echoes have been identified: The echoes are primarily due to isotropic scattering from 70 to 85 km in altitude in summer, whereas they are mainly due to specular scattering from 60 to 70 km in other seasons. Clear annual variabilities have been observed in both occurrence frequency and intensity of the echoes. The upper end of summertime mesospheric echoes seems to be located just below the summer mesopause. An interannual variability of summertime mesopause height has also been suggested.¿ 1997 American Geophysical Union