Budesonide, as one of the inhaled glucocorticosteroids, is widely used in the treatment of asthma by pulmonary delivery. The purpose of this study was to prepare ultra-fine budesonide particles by antisolvent precipitation for dry powder inhalation. Both methanol and acetone were used to make the budesonide solution, and water was chosen as the antisolvent to induce precipitation. Hydroxypropyl cellulose and tyloxapol were added as the stabilizers. The results revealed that crystals of rectangular shape could be obtained from an acetone-water system while elliptic particles were obtained from a methanol-water system. They both had a flaky morphology, no more than 5 mu m in length and 300 nm in thickness, and were formed into agglomerates. When the stabilizers were present, uniform spindle or ellipsoidal particles less than 5 urn in diameter could be prepared. All the prepared particles had the same crystalline structure as the commercial budesonide product, as assessed by X-ray diffraction. In. vitro evaluation with an Aerolizer inhaler and a multistage liquid impinger (MSLI) showed that the flaky particles had better aerosol performance, because they both achieved a FPFemitted value of over 69%. However, the spindle or ellipsoidal particles had poor dispersibility, because of FPFemitted values of 23 +/- 2% and 26 +/- 3%, respectively.