Oxides of nitrogen (NOx) produced in nuclear fireballs could catalytically destroy stratospheric ozone. Since the NOx would be deposited in the upper troposphere and lower stratosphere below the level of maximum ozone concentration, earlier one-dimensional model results showed that the potential ozone destruction rate was limited by the slow rate of vertical diffusion of NOx into the stratosphere. In the current study, the presence of a massive amount of smoke which absorbs solar energy in the upper atmosphere introduces three important changes. First, solar-driven lofting of smoke-filled air displaces ozone-rich stratospheric air with ozone-poor air from the troposphere; at the same time ozone from the northern hemisphere is shifted into the southern hemisphere. Secondly, the modified large-scale circulation rapidly pushes NOx upward, which mixes NOx into the ozone layer much more quickly than previously thought. Finally, the heating of the stratosphere caused by the solar heating of the rising smoke increases the rates of catalytic chemical reactions that destroy ozone. Thus, NOx acts as a chemical catalyst and smoke acts as a thermal catalyst for ozone destruction. The results of simulation using general circulation model (GCM) suggest a rapid ozone depletion in the northern hemisphere. The smoke-induced transport alone can reduce the O3 column by 15--20 Dobson units between the tropics and 60¿N after 20 days of simulation. With the chemical reactions included, ~15% of ozone is depleted between 25¿N and 75¿N after 20 days. ¿ American Geophysical Union 1990