Drug delivery is a term that refers to the delivery of a pharmaceutical compound to humans or animals. Most common methods of delivery include the preferred non-invasive oral (through the mouth), nasal, pneumonial (inhalation), and rectal routes. Many medications, however, cannot be delivered using these routes because they might be susceptible to degradation or are not incorporated efficiently. For this reason, many protein and peptide drugs have to be delivered by injection. For example, many immunizations are based on the delivery of protein drugs and are often done by injection. Current efforts in the area of drug delivery include the development of targeted delivery in which the drug is only active in the target area of the body (for example, in cancerous tissues) and sustained release formulations in which the drug is released over a period of time in a controlled manner from a formulation. This new book focuses on worldwide research on drug delivery and targeting at the molecular, cellular, and higher levels.