The contributions in this special issue clearly demonstrate the broad range of problems involved in the subject of marine biological diversity. One central theme, however, is the need for accurate identification of the organisms being studied. Whether questions investigated involve ecosystem function or the extent of mixing in a gene pool, it is essential first to know what lives where. This requirement has recently been voiced eloquently by the systematics community (Systematics Agenda 2000, 1994) in a volume that also summarizes the components of the science of systematics, such as alpha-level taxonomy and phylogenetic analysis. The importance of systematics and taxonomy has been highlighted by a National Academy of Sciences panel report on marine biodiversity (National Academy of Sciences, 1995). A thorough review and proposed world strategy for understanding and preserving marine biodiversity (Norse, 1993) also emphasized the need for good taxonomic knowledge and the scientific community’s increasing difficulties in fulfilling that need.