Tailoring or modulation of drug release from delivery systems comprises a major area of research in pharmaceutical field where the primary objective is to either sustain drug release or to design orodispersible tablets. This objective can be successfully achieved by use of a class of natural excipients - gums and mucilages. These polysaccharidic plant-derived biopolymers because of their unique swellability in aqueous medium can exert a retardant effect on drug release or can act as superdisintegrant, depending on the concentration used in the formulation. Mechanism of drug release from hydrophilic matrices consisting of gums and mucilages is based on solvent penetration-induced polymer relaxation, diffusion of entrapped drug followed by degradation or erosion of the matrix. The degree and time-scale of swelling contributes significantly to the kinetics of drug release. Drug diffusion from polysaccharidic hydrogel may be of either Fickian, Case II or anomalous transport type. The book has been designed to highlight on the bifunctional aspect of the natural gums primarily because of their concentration-dependent effect on drug release and their high degree of swellability.