The aim of the present study was to design and evaluate in situ gelling system for oral sustained release drug delivery of Famotidine, which was selected as a model drug due to its short biological half-life (2-3 hrs) and as an H2 receptor antagonist to be released in stomach. On the basis of the preliminary trials, a 32 full factorial design was employed to study the effect of independent variables, concentration of pectin (X1) and concentration of CaCl2 (X2) on dependent variables like viscosity, drug content, Q50, Q80 and similarity factor. Main effects and interaction terms of the formulation variables could be evaluate quantitatively by a mathematical model. It was found that both the pectin and concentration of CaCl2 had significant impact on viscosity, drug content, Q50, Q80 and similarity factor (f2) of the system. In-vitro release study revealed that drug released from the insitu gel followed non-fickian diffusion. In vivo study for the selected batch of sodium alginate was carried out by pylorus legation method in rats, which showed gel formation in gastric juice and reduction in ulcer index. Stability study was also carried out for three months, which showed no major changes from their initial state.