The atmospheric importance of carbon dioxide, methane, nitrous oxide, and chlorofluorocarbons is discussed. Atmospheric concentrations of these species have increased because of human activities. Sources, lifetimes, atmospheric budgets, and global warming potentials are presented for the key trace gases. Nitrous oxide, a recently discovered industrial emission byproduct, is examined for its role in stratospheric ozone chemistry and global warming. The atmospheric chemistry of trace gases illustrates many fundamental chemical principles that help engender student interest. These topics are suited for introductory chemistry classes, as well as for advanced courses.