The purpose of this study was to prepare ultrafine beclomethasone dipropionate (BDP) powder via antisolvent precipitation without any surfactants. Various solvents were screened to determine the suitable system for optimum processing while deionized water was kept as the antisolvent. Methanol was selected as the solvent, because a higher degree of supersaturation could be achieved. Several experimental parameters, such as the volume ratio of solution to antisolvent, the concentration of BDP-methanol solution, the temperature, and the stirring speed and time, were investigated in the methanol-deionized water system. The results showed that the yielded powder had a mean particle length of 850 nm and 85% of the particles were distributed in the range of 0.2-1.2 mu m, whereas the raw particle size was 2.13 mu m, ranging in size from 0.2 mu m to 12 mu m. Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) analysis indicated no change in chemical group structure and crystal structure during the process. In addition, a process recovery rate of > 99.99% was obtained.