In this article adapted from PharmaVenture#8217;s Spring/Summer 2007 Drug Delivery Report, Murat Karabiyikoglu looks at transdermal drug delivery (TDD) systems, which, although they have a relatively short regulatory history, have become a proven technology over the past two decades. The benefits of and challenges facing TDD systems are examined, along with the various approaches that have been taken #8211; which include using formulations that increase skin permeability, packaging drugs into particulate carrier systems, and increasing skin permeability by physical means, such as electroporation or the use of micro-needles. The progress that has been made in three areas, pain management, diabetes management and vaccination, is outlined, and some of the deals that have been made in these areas are noted.