Objective: h.pylori eradication requires delivery of the antibiotic locally in stomach. pediatric and geriatric compliance by ease of administration compared to solid dosage form and by reduced dosing frequency can be achieved by combination of levofloxacin hemihydrate and famotidine in liquid dosage form with increased residence time. method: different formulations were prepared by varying the concentrations of sodium alginate and different grades of hydroxy propyl methyl cellulose (hpmc k4m, hpmc k15m, hpmc k100m, and hpmc k100m cr). these formulations were evaluated for ph, drug content, viscosity, gel strength, in vitro buoyancy, and in vitro drug release. box-behnken design was used to check effect of varying concentration of sodium alginate (x1), hpmc k4m (x2), and calcium carbonate (x3). a 32 factorial design was applied to check the effect of varying concentration of sodium alginate (x1) and hpmc k100m cr (x2) on the dependent variable i.e. viscosity, floating lag time, gel strength , time required for complete release (t100) as dependent variables. kinetics of drug release, regression analysis and analysis of variance were performed. the results of the f- test were used to select the most appropriate model. result: all formulations (b1-b15) failed to sustain the drug release upto 12 h. formulations (f2–f9) showed floating within 10 sec and had total floating time of more than 24 h. concentration of sodium alginate and hpmc k100m cr had significant influence on floating lag time, % drug release. formulation f9 was considered optimum with sodium alginate (2%w/v) and hpmc k100m cr (1.25%w/v), it gave release upto 12 hours. conclusion: floating in situ gelling system can be formulated using sodium alginate as a gelling polymer to sustain the drug release for 10 to 12 h with zero-order release kinetics.