Abstract: Almost all newly designed drugs (new chemical entities) demonstrate problematic aqueous solubility and/or permeability through biological membranes, i.e. they show poor bioavailability. One of the progressive ways for increasing bioavaibility is a technique of nanoparticles preparation, which allows many drugs to reach the site of action. Risedronate sodium (Biopharmaceutical Classification System class III) was chosen as a model compound with high solubility and low permeability. Nanoparticles of risedronate sodium are stabilized by polyethylene glycol or sodium carboxymethyl dextran. All prepared samples were measured by dynamic light scattering, and it was found that the particle size ranged from 2.8 to 9.1 nm.