The interest of the use of supercritical fluids, especially supercritical CO2, for particle engineering over the last years has received attention from the pharmaceutical industry. Supercritical fluids can be used in different clean technologies to achieve high supersaturation, and consequently small crystalline particles with a narrow particle size distribution can be produced. This article aims to provide a compilation of old and new supercritical fluid as solvent or antisolvent techniques for drug processing and their fundamentals in terms of crystallization, thermodynamics and modelling results. (C) 2012 Elsevier B.V. All rights reserved.