Photochemical calculations along ''diabatic trajectories'' in the meridional plane are used to search for the cause of the dramatic springtime minimum in Antarctic column ozone. Results indicate that the minimum is principally due to catalytic destruction of ozone by high levels of total odd nitrogen which are in accord with column sum observations of NO2 (between 20 and 35 km) made in the Antarctic. Calculations suggest that these levels of odd nitrogen are transported to the lower stratosphere from the mid to upper stratosphere and lower mesosphere. This transport occurs within the polar vortex and during the polar night. The possibility that these odd nitrogen levels are related to the 11-year solar cycle and are increased by enhanced formation in the thermosphere and mesosphere during solar maximum conditions is discussed. Analysis of satellite data (LIMS, SME, SAGE, SAGE II) establishes significantly increased levels of stratospheric total odd nitrogen for the 1979--1984 time period, particularly at the midsouthern latitudes. Calculations suggest that these mid-latitude increases in odd nitrogen contribute significantly to the recently reported mid-latitude ozone decreases. The persistent reoccurrence of the Antarctic ozone minima into the mid-1980s is related to this growth of odd nitrogen. Transient planetary wave activity near the onset of the final warming is found to significantly moderate the formation of the minimum in column ozone. Chlorine species at double the present atmospheric levels are shown to have an insignificant effect if only homogeneous processes are considered. If heterogeneous chlorine reactions are considered, the catalytic destruction of ozone by the odd nitrogen is slightly inhibited between 20 and 30 km. Below 20 km the catalytic destruction of ozone due to an odd hydrogen and odd chlorine cycle may be fostered by the heterogeneous reactions but this cycle contributes only modestly to the calculated ozone column sum destruction.