The incorporation of active materials in a package or matrix to effect controlled or sustained release of drugs to a targeted area is of high research interest. The nine review articles by leading researchers in this book examine from a multidisciplinary perspective the newest systems and phenomena in this fast-moving field. Topics considered are span polymers (bioactive polymers, biodegradable polymers), microcapsules, biomolecules (liposomes), skin (trans-dermal delivery) and novel drug delivery systems (osmotic pumps). Throughout these discussions the focus is placed on the controlled release of active substances in both time and space (delivery rate and site) to obtain a therapeutic or desired effect.