Naproxen, a poor water-soluble drug, was taken as a model to study the influence of water-soluble carriers (lactose and polyethylene glycol) on drug release from hydroxypropyl methylcellulose (HPMC) matrix tablets. This study demonstrated that the release profile of naproxen from HPMC matrices remained unchanged when lactose or polyethylene glycol 4000 were added to the same drug and polymer concentrations. These data were confirmed by the results of water uptake studies. Due to the higher water solubility of PEG4000, the erosion of compressed mixtures of HPMC K100M/PEG4000 (1: 1) was higher than the erosion of tablets containing the same proportion of lactose.