The objective of this study was to develop a sustained release matrix tablet of aceclofenac usinghydroxypropyl methylcellulose (HPMC K15M and HPMC K100M CR) in various proportions as release controllingfactor by direct compression method. The powders for tableting were evaluated for angle of repose, loose bulkdensity, tapped bulk density, compressibility index, total porosity and drug content etc. The tablets were subjected tothickness, weight variation test, drug content, hardness, friability and in vitro release studies. The in vitro dissolutionstudy was carried out for 24 hours using United States Pharmacopoeia (USP) 22 paddle-type dissolution apparatus inphosphate buffer (pH 7.4). The granules showed satisfactory flow properties, compressibility index and drug contentetc. All the tablets complied with pharmacopoeial specifications. The results of dissolution studies indicated that theformulations F-2 and F-3 could extend the drug release up to 24 hours. By comparing the dissolution profiles with themarketed product, it revealed that the formulations exhibited similar drug release profile. From this study, a decreasein release kinetics of the drug was observed when the polymer concentration was increased. Kinetic modeling of invitro dissolution profiles revealed the drug release mechanism ranges from diffusion controlled or Fickian transport toanomalous type or non-Fickian transport, which was only dependent on the type and amount of polymer used. Thedrug release followed both diffusion and erosion mechanism in all cases. The drug release from these formulationswas satisfactory after 3 months storage in 40°C and 75% RH. Besides, this study explored the optimum concentrationand effect of polymer(s) on acelofenac release pattern from the tablet matrix for 24 hour period.Key words: Aceclofenac; sustained release; hydrophillic matrix; HPMC; direct compression.DOI: 10.3329/dujps.v8i1.5332Dhaka Univ. J. Pharm. Sci. 8(1): 23-30, 2009 (June)