The focus of the present study is on the temperature-dependent behavior of hydroxypropyl methylcellulose (HPMC) solutions at various ionic strength levels. Such behavior is then introduced into the study of tablet dissolution with the aim of explaining why ionic strength could vary the dissolulion rate or cause the tablets to disintegrate. The results show that increasing the concentration of solute in the dissolution media will affect the thermal property of hydrated HPMC and then have an effect on the matrix tablets dissolution process. Of the thermal property, reduction of the cloud point is believed to have some relationship with the decrease of the dissolution rate, and decline of the thermal gelation temperature (TGT) might be responsible for the disintegration of the matrix tablets. A "gel out" process concerning the mechanism of the disintegration has been put forward, and a rheological method to test the lower critical solution temperature (LCST) is also presented. (c) 2006 Wiley Periodicals, Inc.