Solvent-free microparticles, loaded with bovine serum albumin as a model protein, were produced using a novel supercritical (SC) fluid-based coating technology. Coating material consists either of trimyristin (Dynasan(R) 114) or of Gelucire(R) 50-02. Microparticles obtained were characterized as regards their morphology, protein content and in vitro release pro le. A discontinuous coating made of micro-needles of trimyristin led to an initial burst release of similar to70% in 30 min. However, a prolonged release of the BSA could be achieved in a phosphate buffer solution at 37degreesC over a 24 h period from particles coated with Gelucire(R) 50-02. Furthermore, it was shown that BSA does not undergo any degradation after SC CO2 treatment under the conditions used in the coating process.