The dynamics of the optical parameters of stratospheric aerosol produced by the Mt. Pinatubo eruption is given. Measurements were carried out using a two-wavelength lidar with operating wavelengths of 532 and 1064 nm. The processing procedure of the data obtained with two-wavelength polarization laser sounding is described. The aerosol backscattering coefficient and depolarization coefficient at a wavelength of 532 nm and the ratio of the backscattering coefficients taken at two wavelengths are given in the form of isolines in the height-time plane. Possible temporal transformations of stratospheric-aerosol microphysical characteristics governing variations in the optical parameters are discussed.