We successfully performed the micronization of some Cephalosporinic antibiotics by Supercritical AntiSolvent (SAS) precipitation from Dimethylsulfoxide (DMSO) and evaluated the effect of temperature, pressure, concentration of the liquid solution and carbon dioxide molar fraction on the precipitation process. In particular, we varied temperature from 40 to 60 degrees C, pressure from 90 to 180 bar, concentration of the liquid solution from 10 to 90 mg/mL and CO2 molar fraction from 0.5 to 0.98. We obtained different morphologies of precipitates: sub-microparticles, microparticles, balloons (micrometric empty shells) and large crystals. We tried to explain how the presence of solute modifies the vapor-liquid equilibria (VLEs) of the system DMSO-CO2 and to relate the different morphologies observed to the position of the process operating point with respect to the ternary system mixture critical point (MCP). Particle dimensions range from 0.1 to 14 mu m for spherical particles and from 3 to 50 mu m for balloons. (c) 2006 Elsevier B.V. All rights reserved.