The drugs incorporated in controlled release drug delivery systems shows variations in bioavailability due to their selective absorption from specific part of stomach and upper gastro-intestinal tract. In this book, various gastro-retentive approaches have been described for increasing therapeutic performance of drugs having absorption potential from stomach. A major focus has been given on the hydrodyanamically balanced systems, its formulation aspects and effects of excipients and processing parameters. The various types of gastro-retentive drug delivery systems have been well illustrated with diagrammatic illustrations wherever necessary. Also major attention has been given on evaluation of these drug delivery systems. The currently available gastro-retentive drug delivery systems in market have been described. The future potentials of these drug delivery systems have been presented. This book will be useful for the students at graduate level, post graduate students and research scholars for understanding the basics of gastro-retentive drug delivery systems.