The annual mean and the annual amplitude of ozone have been derived from ozone measurements from the SBUV and SBUV/2 spectrometers on board the Nimbus-7 and NOAA-11 satellites. These values differ significantly from values calculated using a two-dimensional model of stratospheric photochemistry and dynamics with standard chemistry. We have found that the differences between the calculated and data-derived values are considerably improved by changing the partitioning in the Cly family to create a larger reservoir of HCl and reducing ClO. This is accomplished by including a channel for the products HCl+O2 from the reaction ClO+OH in addition to the products Cl+HO2. This partitioning also improves the agreement between the calculated and measured values of ClO/HCl ratio. ¿ American Geophysical Union 1993