Production of coprecipitated microparticles is an ambitious application of supercritical antisolvent precipitation (SAS). In this work, coprecipitates of beta-carotene (BC) and polyvinylpyrrolidone (PVP) have been successfully obtained using this technique. Nanostructured microparticles in the range 12.4 mu m were obtained, varying the polymer molecular weight (10 000 and 40 000 g/mol), the polymer/drug ratio (from 10/1 to 20/1), the operating pressure (from 85 to 100 bar), and the total concentration in the liquid solution (from 3 to 7 mg/mL). In particular, at 85 bar, 40 degrees C, 5 mg/mL, with a PVP/BC equal to 10/1, and using the polymer with the lower molecular weight, well-defined coprecipitated microparticles were obtained. Particles produced operating at these conditions showed a vitamin dissolution rate 10 times faster than the one of unprocessed BC, confirming the effective coprecipitation, and the increase of the beta-carotene dissolution rate. The precipitation process and the mechanisms involved are also discussed.