The present invention provides a medicinal aerosol suspension formulation for MDI administration, comprising: a) micronised pa-agonist； b) micronised corticosteroid； c) a siib-therapexrtic quantity of a moisture-scavenger excipient； and d) a HFA propellant； wherein (a), (b) and (c) and their respective relative amounts are selected such that they associate to form floccules having a density substantially the same as that of the HFA propellant.
