Purpose: Currently there are a number of technologies available that have been used to provide sustained release dosage forms and some of these involve the use of a wide range of polymers. This present research describes an investigation of the effects of formulation and processing parameters on a floating matrix controlled drug delivery system consisting of a poly (styrene-divinyl benzene) copolymer low density powder, a matrix-forming polymer(s), drug, and diluents (optional). Methods: The tablets were prepared by the direct compression technique, using hydrophilic matrix polymers HPMC K4M, HPMC K15M, HPMC K100M, sodium alginate, psyllum, sesbania gum, guar gum, and gum acacia, with or without low density copolymer. Tablets were physically characterized and evaluated for in vitro release characteristics for 8 h in 0.1 mol/l HCl at 37˚C. The effect of the addition of low density copolymer and the drug release pattern were also studied. The release rate was modified by varying the type of matrix-forming polymer, the tablet geometry (radius), and the addition of water-soluble or water-insoluble diluents. At the same time, different concentrations of low-density copolymer were taken to examine any differences in the floating lag-time of the formulation. The in vitro release mechanism was evaluated by kinetic modeling. The similarity factor, floating lag-time, and t₅₀ and t₉₀ were used as parameters for selection of the best batch. Results: The tablet eroded/swelled upon contact with the release medium, and the relative importance of drug diffusion, polymer swelling and tablet erosion on the resulting release patterns varied significantly with the type of matrix forming polymer. The highly porous copolymer provided a low density and, thus, excellent in vitro floating behavior of the tablets at a concentration of 15% (w/w). Conclusion: It was established that floating behavior of the low-density drug delivery systems could be successfully combined with accurate control and prolongation of the drug release patterns.