From its first commercial appearance in the 1950’s, the chlorofluorocarbon (CFC) propelled MDI enjoyed steady growth until the late 1980s, when the discovery of stratospheric ozone depletion forced a fundamental change to an alternative class of propellants, the hydrofluoroalkanes (HFAs). The conversion has been challenging, and it is only recently that the last CFC-propelled MDIs have been manufactured. pMDI remains a core treatment methodology for a number of inhaled medicines and continues to see growth worldwide. Having successfully met the ozone-depletion challenges and negotiated the HFA transition, additional environmental regulations relating to global warming potential, are coming to the fore. Although provision for continued pMDI usage has been made in the relevant environmental legislation, work is on-going to minimise the potential environmental impact associated with pMDI use including an appraisal of potential new propellant options.