Process for preparing sterile suspensions for inhalation comprising an active ingredient insoluble in water and wherein at least 80% of the particles of said active ingredient have a diameter between 3 and 5 μm, comprising the following stages: dissolving the active ingredient in the minimum quantity of an alcoholic solvent, optionally in the presence of a polyol and adding at least one surfactant, filtering the solution obtained in the previous stage through a sterilizing filter, adding the solution from stage (b) to sterile water under sonication to directly obtain a suspension wherein the particles have a reduced diameter.
