[Show abstract][Hide abstract] ABSTRACT: Microparticulate systems of aceclofenac were prepared by modified solvent evaporation method using different variables such as polymer (cellulose acetate): drug ratios (1:9, 1:6, 1:3, and 1:1), agitation speeds (500-1500 rpm) and stirring time (5-15 min). The effects of processing variables were evaluated by microparticle size and entrapment efficiency. The average microparticle size increases from 80.2 ± 1.45 to 97.3 ± 2.06 µm with increase in the polymer concentration while reduces with increase in agitation speed and stirring time; and at the higher speed gives irregular shape of particles. The highest entrapment efficiency, size uniformity, angle of repose (23.6 ± 0.3 degree) and compressibility index (13.8 ± 0.7%) of microparticles were found with 1:6 (polymer: drug ratio), at 1000rpm and 10min stirring time among all microparticles. The in-vitro drug release study was carried out with prepared microcapsules (AC-1 to AC-4) of various polymer concentrations and optimized processing variables and compared with conventional and SR tablets. The conventional tablet and SR tablet releases maximum drug within 3 and 6h respectively while microparticulate system releases more than 12h. All formulations followed first order release kinetic and diffusion controlled drug release.