Today R134a is the worlds number one refrigerant for automotive air conditioning (A/C). Alternatives to be more environmentally friendly are so called ‘natural fluids’. There are options with water and ammonia in vapor compression and sorption systems, or nitrogen and helium as working fluids in different gas cooling cycles. The following options have already been investigated and tested more seriously: air as working fluid in Joule process systems; hydrocarbons as working fluid in vapor compression systems; carbon dioxide (CO2) transcritical vapor compression systems.These alternatives are either processes using flammable or toxic refrigerants or needing the development of totally new equipment because the type of process is new for mobile A/C or the pressure level is extremely increased compared with recent systems. Beside this there is also the chance to use the environmentally friendly CO2 as refrigerant together with other refrigerants. This will reduce the pressure and the system can operate in a lower pressure range and with almost the same kind of components as the recent R134a systems. The different options will be discussed.