Ground-based measurements of stratospheric NO2 made from three Antarctic sites in 1986 and 1987 show the effect on the NO2 column at each station of photochemical changes brought about by changing season, superimposed on the dynamically induced intrusion of lower latitude NO2 enriched air. At the special location of South Pole station, NO2 slant column changes can be observed at effectively constant solar zenith angle, and show the effects of a horizontal gradient in the NO2 distribution. ¿ American Geophysically Union 1988