With the phase-out of R-22, system manufacturers are forced to choose new HFC refrigerants that eliminate the harmful chlorine, while offering the best system efficiency possible. The following paper discusses the factors that Emerson Climate Technologies feels are most important for meeting this challenge. “Refrigerants for Residential and Commercial Air Conditioning Applications” starts with a brief introduction and background and then focuses on environmental drivers and a regulatory update. Next come the criteria for refrigerant selection, followed by a presentation of transitional refrigerants (HCFCs), chlorine-free refrigerants (HFCs), halogen-free refrigerants and lubricants. After pointing out responsible-use principles, the authors propose a future direction and offer a glossary of terms, as well as an appendix with suggestions for further information on the subject.