The kinetics of stratospheric accumulation of sulfuric-acid aerosols and the variation of the ozone content at altitudes from 27 to 32 km after a volcanic eruption are modelled. The chemical scheme includes the 10 main reactions of the oxygen cycle of ozone and SO2 photooxidation. The peculiarity of this scheme is its account of SO2 photooxidation by ozone. Satisfactory agreement between the calculated and experimental data on temporal variations of sulfuric acid aerosols concentration after a volcanic eruption was obtained.