The crystals of pharmaceuticals, e. g. ibuprofen and ketoprofen, were directly modified during the crystallization process with acrylic polymer (Eudragit^®) using a novel spherical crystallization technique. The resultant crystals were microspheres agglomerated with the polymer, which were highly flowable and compressible. The drug release rate from the microspheres was pH-dependent and controlled quantitatively by the type and the amount of the polymer employed. In addition, the microspheres improved the bioavailability of the drug in dogs.