Stratospheric in situ aerosol and ozone measurements aboard the NASA-operated ER-2 high-altitude research aircraft from August 1991 to May 1993 provide an opportunity to document the temporal evolution of the correlation between the stratospheric aerosol and the ozone from shortly after the Mount Pinatubo eruption until almost two years later. The observations show that at midlatitudes a linear relationship evolves between aerosol surface (or number) mixing ratios and ozone at latitudes ranging from slightly above the tropopause to 14-16 km. This correlation is linear for values of ozone from 200 to 1300 parts per billion by volume and for potential temperatures between 310 K and 467 K. The linear correlation persisted from late December 1991 until early March 1992 but degraded by October 1992. ¿ American Geophysical Union 1995