The present invention provides a medicinal aerosol suspension formulation for MDI administration, comprising: a) micronised ² 2 -agonist b) micronised corticosteroid c) a sub-therapeutic 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.
