By means of calculations with a one-dimensional photochemical-diffusive model of the atmosphere a theoretical estimate is given of the present and the possible future impact of large sections of the chlorocarbon industry on the ozone layer. Our estimates for 1976 are that past chlorocarbon emissions may be responsible for a 1.5% reduction in the global total ozone content (0.8% by CFCl3 and CF2Cl2, 0.5% by CCl4, and 0.2% by CH3CCl3). This estimate was obtained by comparison with the ozone content of a model atmosphere without industrial chlorocarbon emissions. The effect of the nonindustrial gas CH3Cl can best be described by stating that without CH3Cl, there would be almost 1% more ozone in the atmosphere. Considerable attention should also be given to the atmospheric effects of expanding uses of CH3CCl3. The potential impact on the ozone layer of CHFCl2 and CHF2Cl emissions is also discussed. However, there are too many uncertainties regarding the tropospheric concentrations of OH and its role as a scanvenger to assess the effect of a number of chlorocarbon compounds reliably. The effect of other chlorocarbon compounds (C2Cl4, C2HCl3, C2H5Cl, C2H4Cl2, CHCl3) on the ozone layer is estimated as being comparatively neglible. Model-calculated vertical distributions of a large number of constituents are compared with observations. Substantial deviations between some theoretical and reported concentrations exist, especially for NOx, CO, and ClO. Uncertainties in our knowledge of strastopheric chemistry are discussed. It is concluded that these uncertainties are sufficiently numerous to take the given predictions of ozone reductions with some reservations.