The replacement of chlorofluorohydrocarbon propellants in medical aerosols is of the utmost importance to the pharmaceutical industry. A number of formulations have been investigated.The present invention provides a medical aerosol formulation comprising a particular medicament, a fluorocarbon propellant and 6 to 25% w/w of the total formulation of a polar co-solvent, such formulation being substantially free of surfactant. Canisters suitable for delivering such a pharmaceutical formulation are also provided.