Current efforts in the area of drug delivery include the development of modified release technologies for improving product efficacy, safety, and patient compliance. Polymeric excipients play a critical role in determining the mechanism and rate of drug release from the solid oral dosage forms. Regardless of the physicochemical properties of drug molecules and physiological conditions of the body, it is now possible to achieve site-specific delivery of drugs in a sustained manner. This chapter highlights the polymeric excipients that are widely used in modulating the release and enhancing the oral absorption of drugs.