The supercritical-assisted atomization (SAA) process is a novel technique proposed recently to prepare micro-particles with controlled particles size distribution suitable for aerosolizable delivery. It has shown a great potential in drug micronization especially for water-soluble drugs. Cefadroxil micro-particles were prepared successfully from water-ethanol mix-solvent by SAA process. The influence of the operation parameters, including the pressure and temperature in the mixing vessel, the solution concentration and the solution feed rate, on the particle morphology, size and size distribution was investigated in detail. The results show that the concave cefadroxil micro-particles suitable for pulmonary drug delivery could be prepared by SAA process in certain conditions. The pressure in the mixing vessel and the solution feed rate are two most effective parameters while the solution concentration is the next. The temperature in the mixing vessel has a little effect. The particle characteristics could be controlled by adjusting operation conditions. The optimal operation parameters for preparing cefadroxil micro-particles in the scope of this work are: the pressure of 10 MPa and the temperature of 60 degrees C in the mixing vessel, the solution feed rate of 3 ml/min, and the solution concentration of 4 mg/mill. (C) 2008 Elsevier B.V. All rights reserved.