This book initially provides a review of controlled drug delivery systems and an overview of microencapsulation methods with emphasis on the emulsion solvent removal methods. The book then presents studies conducted on producing microspheres containing commonly used drugs such as Theophylline, Piroxicam and Propylthiouracil. The book also discusses various formulation and processing parameters affecting microsphere-drug products. Such factors include the effects of polymer solution phase viscosity and molecular weight the on the properties microspheres. It also discusses the use of single and combinations of polymers of different properties that are manipulated in a way to achieve goals such as controlled release, enteric properties, masking taste or drug and body protection. Interesting results were found in many preparations and many are published in international journals.