Between 9 December 1997 and 5 February 1998 during Leg 177, seven sites were drilled in the eastern Atlantic sector of the Southern Ocean. This marked the return of the JOIDES Resolution to the Southern Ocean after an almost 10-yr hiatus in drilling of the high southern latitudes. We targeted this region because paleoceanographers, paleoclimatologists, and geochemists have become increasingly aware that processes occurring in the Southern Ocean have played a major role in defining the Earth's climate system throughout the Cenozoic. Leg 177 sites are arrayed along a north-south transect from 41° to 53°S (Fig. F1), crossing each of the major surface frontal boundaries of the Antarctic Circumpolar Current (ACC). Water depths range from 1974 to 4620 m, intersecting most major subsurface water masses in the South Atlantic (Fig. F2). We succeeded in accomplishing nearly all of our coring objectives, recovering a total of >4000 m of sediment ranging in age from the middle Eocene to Holocene. At most sites, multiple holes were drilled to ensure complete recovery of the stratigraphic section. A complete description of the Leg 177 sediments recovered and shipboard analyses performed is given in the Leg 177 Initial Reports volume (Gersonde, Hodell, Blum, et al., 1999). At the time of writing, 4 yr has elapsed since we set sail on Leg 177. Shipboard scientists have had an opportunity to analyze samples in their laboratories, and postcruise scientific results are now being published. Our purpose here is to present an overview of Leg 177 science to date by synthesizing individual reports and evaluating our progress toward meeting the overall leg objectives. We have also included some results obtained on piston cores retrieved by the Polarstern and Thomas G. Thompson (TTN057) as part of the site survey for Leg 177 because many of these cores have been spliced with the upper sections of Ocean Drilling Program (ODP) cores to obtain complete sections. Most of the Leg 177 papers are contained within this volume or in two special issues of Marine Micropaleontology (July 2002, Volume 45, Issues 3-4, pp. 191-402) and Palaeogeography, Palaeoclimatology, Palaeoecology (July 2002, Volume 182, Issues 3-4, pp. 145-355) (Gersonde and Hodell, 2002), designed to highlight the biostratigraphic and paleoceanographic results of Leg 177, respectively. Many papers have also been submitted or published in other mainstream journals. The bibliography at the end of this chapter contains a list of Leg 177 papers that was complete at the time of publication and will be updated continually on ODP's web site (www-odp.tamu.edu/publications/pubs_ct.html). The CD-ROM included with this booklet contains the Leg 177 papers and data reports submitted to ODP and completed by the time of printing.