The use of skin as a drug delivery route for systemic therapy has been demonstrated to be capable of avoiding the hepatic first-pass effect thus achieving higher systemic bioavailability of drugs and to decrease the dosing frequency required for oral treatment. The present book is, in fact, an outgrowth of the experimental findings of research in the development of controlled release transdermal formulation of trazodone hydrochloride. The book is primarily intended to serve as a reference book to provide guidelines to the new researchers from the academia and industrial communities in the field of transdermal drug delivery systems and to stimulate new ideas about development strategy. The methodology may differ from problem to problem, yet the basic approach towards transdermal research remains the same. I shall feel amply rewarded if the book proves helpful in the accomplishment of formulative as well as hypothesis testing research studies in the area of transdermal drug delivery systems.