Effects of inorganic salts on disintegration of hydroxypropylmethylcellulose (HPMC) matrix tablets have been studied. Adding disintegrants, such as Ac-di-sol^®, Primojel^®, Kolidon-CL^®, or low substituted hydroxypropylcellulose (L-HPC^®) to HPMC matrix tablets had no effect on disintegration property. Disintegration time was improved by adding NaHCO₃, KH₂PO₄, K₂SO₄, KCl, or NaCl to the HPMC tablets as tablet components. On the other hand, addition of Na₂CO₃, or Na₂SO₄ to the tablets showed no improvement of disintegration. The heat of dissolution of inorganic salts that improved disintegration of tablets was endothermic, while that of inorganic salts that did not improve disintegration of tablets was exothermic. These results suggested that the thermal environment and ionic strength inside the tablet might affect the disintegration of HPMC matrix tablets.