We demonstrate that stable microwave-coupled atmospheric pressure nonequilibrium plasmas (APNEPs) can be formed under a wide variety of gas and flow-rate conditions. Furthermore, these plasmas can be effectively used to remove surface contamination and chemically modify polymer surfaces. These chemical changes, generally oxidation and crosslinking, enhance the surface properties of the materials such as surface energy. Comparisons between vacuum plasma and atmospheric plasma treatment strongly indicate that much of the vacuum-plasma literature is pertinent to APNEP, thereby providing assistance with understanding the nature of APNEP-induced reactions.