Stratospheric aerosol contents measured by lidar in Frascati and ozone contents measured by Dobson spectrophotometers and by ozonesondes at geographically close stations in the period following the El Chichon eruption of 1982 have been compared. The total contents as well as the vertical profiles of the two quantities show large, negatively correlated fluctuations. Estimates of the change in the ozone photodissociation frequency due to enhancd scattering by the volcanic aerosol as well as changes in the reaction rates due to heating indicate that radiative processes should be considered amongst the causes of the ozone anomaly. ¿ American Geophysical Union 1987