Polymer microspheres are becoming attractive drug delivery systems due to their biodegradability, non-toxicity and easy administration. In this study, a rosemary extract exhibiting anti-proliferative activity against various human cancer cell lines was encapsulated by polycaprolactone using gas anti-solvent process and solvent evaporation method. The particles were characterized by X-ray diffraction, differential scanning calorimeters analyses and scanning electron microscopy, whereas in vitro release kinetics was determined by the dialysis cell method. Although the fabrication methods seemed not to play an important role in the diffusion rate and release profiles of both loaded samples in aqueous medium, fabricated rosemary extract with gas antisolvent process at 300 bar, 40 degrees C and a flow rate of 20 g/min exhibited a narrow particle size distribution, a lower mean particle size and higher encapsulation efficiency (254.5 nm, 82.8%) compared to the traditional fabrication method (617.5 nm, 62.2%). (c) 2011 Elsevier B.V. All rights reserved.