Since the Industrial Revolution the chemical composition of the atmosphere has changed at a rate unprecedented in recent history. Ozone depletion emerged as one of the most important environmental issues of the 20th century as evidence grew for substantial human influences on the atmospheric ozone abundances over much fo the globe. The science of the ozone layer and its interactions with halogenated chemical compounds are the primary subjects of this book. The volume provides a comprehensive view of the chemical, dynamical, and radiative processes that affect ozone and other chemicals in the stratosphere and mesosphere. Over recent decades our understanding of these processes has increased dramatically. The discovery of the Antarctic ozone hole has shown that human activities can lead to major changes in our environment.