The purpose of this study is to investigate the effect of formulation variables on drug release and floating properties of the delivery system. Hydroxypropyl methylcellulose (HPMC) of different viscosity grades and Carbopol 934P (CP934) were used in formulating the Gastric Floating Drug Delivery System (GFDDS) employing 2 x 3 full factorial design. Main effects and interaction terms of the formulation variables could be evaluated quantitatively by a mathematical model. It was found that both HPMC viscosity, the presence of Carbopol and their interaction had significant impact on the release and floating properties of the delivery system. The decrease in the release rate was observed with an increase in the viscosity of the polymeric system. Polymer with lower viscosity (HPMC K100LV) was shown to be beneficial than higher viscosity polymer (K4M) in improving the floating properties of GFDDS. Incorporation of Carbopol, however, was found to compromise the floating capacity of GFDDS and release rate of calcium. The observed difference in the drug release and the floating properties of GFDDS could be attributed to the difference in the basic properties of three polymers (HPMC K4M, K100LV and CP934) due to their water uptake potential and functional group substitution.