After the previous review [Brune, 1991] of the breadth of scientific activity following reports of an ozone hole over Antarctica and of similar photochemistry over the Arctic, it is surprising to find as rich a literature base for this review. Admittedly, some of the recent publications are new, but belated, reports of studies carried out before 1991, while some are results of ongoing studies. However, there have also been important new developments in stratospheric chemistry, many of which were initiated by the long‐awaited launch of the Upper Atmosphere Research Satellite (UARS) [Reber, 1993], the Second Airborne Arctic Stratospheric Expedition (AASE II) [Anderson and Toon, 1993], the European Arctic Stratospheric Ozone Expedition (EASOE) [Pyle et al, 1994], the NASA High‐Speed Research Program (HSRP) [Albritton et al, 1993], the eruption of Mount Pinatubo [McCormick, 1992], and the Stratospheric Photochemistry, Aerosols, and Dynamics Expedition (SPADE) [ Wofsy et al, 1994]. The review period was also highlighted by observations of the lowest global ozone abundances on record [Gleason et al, 1993], detection of enhanced ultraviolet radiation at the earth's surface [Frederick and Alberts, 1991], examinations of possible strategies for mitigating ozone losses [Cicerone et al, 1991], and direct confirmation of the effectiveness of international agreements limiting the production of ozone‐destroying substances [Elkins et al, 1993].