Vaccine research and development is a heterogeneous and intensely active area, encompassing the development of many different kinds of novel preventive and therapeutic vaccines (eg, against infectious, allergic, and autoimmune diseases, cancer, etc). Included in this is the development of different types of vaccines (eg, DNA vaccines, novel routes of administration, novel adjuvants, and immune system modulation). This poses challenges regarding approaches to preclinical evaluation of these products. Published regulatory guidance has not always kept up with scientific advances and innovation in this area and, at the same time, many vaccine developers are interested in better understanding and meeting regulatory expectations. It was in this context that in June 2007 a workshop was organized and held in Amsterdam (DIA International Workshop on Nonclinical Testing of Vaccines) to discuss the nonclinical aspects of vaccine development. This article provides a short historical overview of preclinical testing of vaccines and reviews and summarizes the discussions held during the June 2007 meeting. Copyright © 2009 Drug Information Association, Inc.