The stratospheric aerosol layer has been monitored from 1982 through 1986 by a lidar in NIES, Tsukuba (36¿N, 140¿E). A strong enhancement in the signals from the stratospheric aerosol layer was observed in 1982 and 1983 as a result of the volcanic aerosols from the El Chichon (Mexico) eruption in March and April 1982. Multiplex thin aerosol layers with ~1-km thickness were observed in the autumn of 1982. Another enhancement in the amount of stratospheric aerosols was observed in the winter of 1985/1986. The origin of the new aerosol layer can be attributed to the eruptions of Nevado del Ruiz (4¿53'N, 75¿22'W) on November 13, 1985. The long-term decay of the integrated backscattering coefficient (IBC) from 1982 through 1986 will also be discussed. The optical thickness converted from IBC observed at Tsukuba in late 1982 was up to about 0.2 which was larger than that observed over North America in the same period. ¿ American Geophysical Union 1991