Lidar observations of the stratospheric aerosol layer have been carried out at Tsukuba and Naha, Japan, and at Lauder, New Zealand. Evolution of the volcanic aerosols originating from the 1991 Mt. Pinatubo volcanic eruptions, and the subsequent trend and seasonal variations of the background aerosols, are evaluated. Stratospheric aerosol drastically increased to about 30 to 100 times of the background level after the eruption, and returned to calm condition after about five years. The e-folding time of the integrated backscattering coefficient of Pinatubo aerosols at the three stations shows similar values between 1.14 and 1.37 years. The column amount of background stratospheric aerosol over Lauder is about 3 times as much as that over Naha, and that over Tsukuba is between the other two sites. Seasonal variation of stratospheric aerosol over Tsukuba shows the largest value and is nearly 10 times as much as that over Naha. The background aerosols over Lauder increased after around 2000. The increasing rate observed over Lauder is about 3.8%/year from 2000 to 2009.