Atenolol is a beta-blockers drug commonly used in the prevention of heart diseases. The aim of this work is to improve its bioavailability modifying its particle morphology by using supercritical carbon dioxide as antisolvent agent. Saturation conditions, at different temperatures, for ternary systems made up with carbon dioxide and solutions of atenolol in methanol, ethanol and isopropanol have been investigated using a variable volume cell. The effect of the presence of the active principle on the vapor-liquid equilibrium for the organic solvent-carbon dioxide system have been considered in order to choose the best operative conditions to perform the antisolvent precipitation process. Atenolot was then processed from different solutions (5%, w/w atenolol-methanol; 5%, w/w atenolol-ethanol and 1.65%, w/w atenolol-isopropanol) by sending the streams in a precipitation chamber firstly in counter cur-rent and later on in equicurrent. Various characterization analyses have been made on the precipitated powders. It is important to note that the release profiles of the precipitated atenolol show a general enhancement of the dissolution rate, compared to the one of the untreated drug. (c) 2005 Elsevier B.V. All rights reserved.