A novel one-step, low energy method, which avoids harsh processing conditions including potentially toxic and chemically reactive cross-linking agents, for the production of hydrophilic drug nanoparticles suitable for dispersion in the hydrofluoroalkane propellants was investigated. Reverse-phase microemulsions were used as the template for the production of nanoparticles. Two microemulsion systems were investigated: water/sodium bis(2-ethylhexyl) sulphosuccinate (AOT)/iso-octane and water/lecithin/propan-2-ol/iso-octane. Nanoparticles were captured by snap freezing with subsequent freeze-drying. Nanoparticles were dispersed in 1,1,1,2,3,3,3-heptafluoropropane (HFA-227) and the aerosol performance of the pressurised metered dose inhaler (pMDI) assessed by cascade impaction. Spherical nanoparticles less than 300 nm in size were produced. Nanoparticles produced using AOT as the surfactant could not be dispersed in HFA-227. However lecithin based nanoparticles could be dispersed in co-solvent modified HFA-227 and produced fine aerosols (Mass Median Aerodynamic Diameter < or = 1.5 microns, fine particle fraction > 58%). This data suggests that a high fraction of the nanoparticles would be deposited (targeted) within the lung with the deposition being mainly alveolar. That is the ideal deposition profile for the systemic delivery of drugs via the lungs.