With a reasonably complete and up-to-date photochemical model of the stratosphere, we find that the calculated stratospheric ozone-column response to chlorine injections is highly nonlinear. The model calculations assume that the background inorganic (or odd) chlorine, Cl X, is due to CH3Cl and CCl4. Additional Cl X is added to the stratosphere by varying input fluxes of CCl2F2 and CCl3F. The sensitivity, ΔO3/ΔCl X, of the stratospheric O3 column to added Cl X is relatively small for Cl X≲3 ppb or ΔCl X≲2 ppb; slight ozone increases with Cl X are possible over a limited range of Cl X if the formation of chlorine nitrate proceeds rapidly. This may have important implications for total ozone-column trend assessment. As Cl X increases beyond 3 ppb, the stratospheric O3 column decreases with Cl X increasingly rapidly. This marked departure from the linearity calculated in past years is largely due to presently accepted faster rates of reaction of OH with HNO3, HNO4, HO2, and H2O2. If stratospheric Cl X increases to about 9 ppb due to continued usage of CCl2F2, CCl3F, and CH3CCl3, the stratospheric O3 column depletion is calculated to be 6.7--9.0%. Principal uncertainties in these calculations, including the rate of formation of chlorine nitrate, the products of its photolysis, and the present day mixing ratio of Cl X are discussed. Calculated ozone decreases due to increased N2O concentrations are also presented.