In the present work the effect of two different diluents namely dicalcium Phosphate (DCP) and maize starch (MS) on the release of aceclofenac from sustained release matrix tablets has been studied. Gum damar (GD), a hydrophobic polymer with significant binding property was used as a release retarding agent. In the present study aceclofenac was used as a model drug for developing sustained release matrix tablets owing to its short biological half life (4 hours) and dosing frequency more than one tablet per day. Matrix tablet of aceclofenac using synthetically prepared hydrophilic polymers (e.g. HPMC) have been reported. However, low cost, ease of availability and non toxic property makes use of natural gums (e.g. gum damar), an alternative approach for development of sustained release matrix tablets. Compatibility between aceclofenac and GD was studied using FTIR. Sustained release matrix tablets of aceclofenac using GD as release retardant were prepared by wet granulation technique. Matrix tablets were prepared using different strengths of GD (10% - 30% w/w) with respect to total tablet weight and two different excipients DCP & MS as diluents. The tablet weight (400mg) and diameter (10mm) was kept constant. The physicochemical properties such as hardness, thickness, friability, uniformity of weight and the drug content of the formulated tablets were estimated The in vitro dissolution profile of the formulated tablets was compared with marketed sustained release aceclofenac tablets. The kinetics of release of aceclofenac from the matrix tablets were found to follow Hixon Crowell cube root law indicating a surface dependent release. The study revealed that GD as release retardant along with MS as diluent show results comparable to that of the marketed sustained release tablets of aceclofenac.