This chapter addresses regulatory issues that have an impact on the pharmaceutical development of delivery systems for medicines to be used in humans. It deals with current European Union (EU) regulations and guidelines relating to the physicochemical/technical aspects of a delivery system which have to be optimized and controlled in vitro in order to achieve a desirable and consistent clinical response in patients. Furthermore, since EU law allows a number of possible routes to market, with some routes being optional and others mandatory, it appears that the EU regulatory picture may be more diverse than that in the United States, and therefore it is appropriate to at least mention the regulatory options.