The role of nitrous oxide (N 2 O) in the global nitrogen cycle is discussed. Nitrous oxide is an important trace component of the Earth's atmosphere with a 120-year atmospheric residence time. It exhibits a global warming potential 310 times that of CO 2 on a per molecule basis, and like CO 2 , its atmospheric concentration is increasing. Nitrous oxide is produced naturally as a byproduct of nitrification and denitrification. There are also several anthropogenic sources. Structural, physical, spectroscopic, bonding, thermodynamic, and solution properties of NO 2 are reviewed. The reactions known to yield N 2 O are surveyed. Fundamental chemical kinetics and mechanisms that lead to its formation are discussed, which emphasize our research involving nitric acid, nitric oxide, and ammonium nitrate as N 2 O precursors. These results are discussed in the context of their relevance to biological and environmental chemistry.