Carbon dioxide is the only fluid which has been applied in producing composite particles by supercritical fluid methods. In the present paper, design of composite particles by supercritical carbon dioxide (SCO2) will be reviewed. The production processes of composite particles by SCO2 are classified based on fluid roles, which are solvent, anti-solvent, solute and reaction medium. In addition, these processes are sub-categorized based on the fluid flow and contact pattern. (C) 2006 Elsevier B.V. All rights reserved.