The purpose of this study was to investigate the effect of different proportions of HPMC polymer in the release of drug from the hydrophilic matrix tablets. Three formulations were made by wet granulation method 450mg Lithium carbonate and 10%, 20% & 30% HPMC were granulated with Ethanolic solution of Eudragit S100, dried and then compressed to formulate the tablets. In vitro studies were conducted on the three formations. All the three formulations demonstrated relatively sustained release behavior but the matrix tables containing 30% HPMC exhibited suitable release kinetics.