Once-daily sustained-release matrix tablets of metoprolol succinate, selective β1- blocker used in cardiovascular diseases were developed.The tablets were prepared by the wet granulation method.Ethanolic solutions of ethylcellulose (EC), polyvinylpyrrolidone K30 were used as granulating agents along with hydrophilic matrix polymer hydroxypropyl methylcellulose (HPMC K100M).The granules were evaluated for angle of repose, bulk d., compressibility index and drug content.The tablets were subjected to thickness, diameter, weight variation test, drug content, hardness, friability and in vitro release studies.The granules showed satisfactory flow properties, compressibility and drug content.All the tablet formulations showed acceptable pharmacotech. properties and complied with inhouse specifications for tested parameters.The results of dissolution studies indicated that batch AH3 (Drug-to-HPMC K100M, Et cellulose solution (4% W/V, as granulating agent) could extend the drug release up to 24 h.Batch AH3 showed highest f2 value 84.95 and MDT 8.9 h similar to that of reference product.The dissolution data were subjected to model fitting anal. and best fitted model was Higuchi model.All the formulations (except batch AH3) exhibited diffusion-dominated drug release.The mechanism of drug release from batch AH3 was diffusion coupled with erosion.