This study had two major objectives. The first was to fill gaps in our understanding of important biological, chemical, and physical processes occurring in the Bay. This information was required to make the best use of existing data and to develop future data needs to further understand the basic functioning of the Bay system. The second objective was to collect a synoptic data set for the entire Chesapeake Bay to be used in future modeling efforts and to establish the present condition of the main Bay at one point in time. Field work for the study was conducted by sixteen scientists on thirteen cruises between 1 May 1980 and 1 June 1981. The synoptic nutrient study was conducted from 8 to 17 July 1980 in conjunction with a circulation study covering the entire Bay from 25 June to 29 July 1980. The process studies were performed at various times and locations dictated by the processes themselves. Subsurface transport of nutrients and phytoplankton were examined in May 1980 in the upper Bay. Sediment nutrient releases and oxygen demand were studied in eight locations in summer 1980 and spring 1981. Nitrogen and silica dynamics were examined in several locations during July, August, and September 1980. Bacterial dynamics were studied in August 1980. The results of these studies added important information to the body of knowledge about Chesapeake Bay.