Supercritical assisted atomization (SAA) was used to produce micronized particles of beclomethasone dipropionate (BDP) to be used for inhalation therapy Methanol, acetone, acetone + water 9% v/v. and methanol + water 4% v/v were tested as liquid solvents to explore their influence on particle size and crystalline structure of the precipitated powder Particles with narrow size distributions (PSD) were obtained by changing the SAA process operating conditions In particular, using acetone + water 9% v/v with a BDP concentration of 90 mg/mL, crystalline particles ranging between 0 2 and 4 7 mu m were produced and 70% by volume of these particles ranged between land 3 ism PSD stability analysis in a wet formulation showed that BDP powder obtained by SAA does not modify over a long period of time The results obtained on the laboratory scale plant were successfully reproduced on a pilot plant and a further refinement of the operating conditions was performed About 30 g of BDP microparticles were produced per batch and a recovery of about 93 wt % of the micronized powder with respect to the injected quantity was obtained The largest volumetric fraction of BDP particles falling in the range 1-3 mu m was 83% on the pilot scale