(1) Owing to its strategic location, rich fisheries and natural resources, the Adriatic Sea possesses a long history of scientific exploration (Cushman-Roisin et al. (2001) provides a comprehensive review). The two volumes of this Adriatic Sea special section contribute to this rich literature by collecting results from a recent period of intense research activity. During 2002-2003, the combined efforts of several large, multi-disciplinary international pro- grams brought an exceptional array of observational and numerical resources to bear on contemporary questions in Adriatic research. Supported by the U.S. Office of Naval Research, NATO, the Croatian Ministry of Science and Technology and the Italian Ministry of the Environment and Ministry of Universities and Research, scientists from several countries pursued interrelated collaborative research programs. Broad-ranging studies included investigations of circulation at kilometer to basin scales, physical and biological response to bora wind forcing, sediment transport and mucilage formation. Extensive numerical efforts contributed to the success of many of these programs, providing interpretation and understanding and, in some cases, extensions into short-term forecasting.