The horizontal distributions of air in the temperature ranges -70¿>T>-77 ¿C, -77¿>T>-85 ¿C and TT>-77 ¿C was confined within the dynamically defined Arctic vortex, with only small fractions appearing outside the chemically defined vortex. In the Antarctic, up to 14% of this air was outside the chemically defined vortex but very little was outside the dynamically defined vortex. After late January (Arctic) and late August (Antarctic), respectively, the chemically defined vortices shrank, being 27% and 20% smaller in February and September. The dynamically defined vortices remained essentially constant in area. There were no occurrences of nominal type II polar stratospheric clouds (PSCs) outside either vortex, however defined. One implication of these results is that heterogeneous conversion of CIONO2 and HCl to reactive forms of chlorine is confined almost entirely to the Arctic vortex, while some such conversion may occur at the edge of the Antarctic vortex. However, small and infrequent areas of air in the range -77¿>T>-85 ¿C did occur immediately outside both vortices, so separating the effects of peel-off, type I PSCs and sulfuric acid aerosol processing may be difficult on occasions. What is clear is that all three processes are intimately associated with the polar night jet stream.