The composition of the atmosphere is determined by emissions, chemical transformations, transport, and removal. Emissions can be natural and man-made and include thousands of different compounds. Chemical transformations occur on time scales ranging from seconds to centuries. Transport on local, regional, and global scales determines the geographic extent of the impact of emissions on atmospheric composition. Deposition is an important removal mechanism for many compounds that is not well understood. Describing all of these processes is important because changes in atmospheric composition affect many issues of societal importance including air quality, the stratospheric ozone layer, climate, and ecosystem function and health. This session provides a general forum for scientists working on Atmospheric Chemistry and Composition. We welcome new research (field work, laboratory studies, modeling, data analysis, etc.) that does not fall under the umbrella of other sessions, as well as reviews and perspectives on important areas of study.