ABSTRACT: The Bermuda Atlantic Time-series Study (BATS) commenced monthly sampling in October 1988 as part of the U.S. Joint Global Ocean Flux Study (JGOFS) program. The goals of the U.S. JGOFS time-series research are to obtain an understanding of the basic processes that control ocean biogeochemistry on seasonal to decadal time-scales, determine the role of the oceans in the global carbon budget, and ultimately improve our ability to predict the effects of climate change on ecosystems. The BATS program was built upon Bermuda's rich history of ongoing open ocean and atmospheric time-series programs, including: Hydrostation S which began in 1954, deep-ocean sediment trap collections which began in 1976, and atmospheric chemistry and deposition measurements which began in 1980. The BATS program samples the ocean on a biweekly to monthly basis, a strategy that resolves the major seasonal patterns and interannual variability. The core cruises consist of a single four-five day cruise in which hydrography, nutrients, particle flux, pigments and primary production, bacterioplankton abundance and production, and often complimentary ancillary measurements are made. This overview focuses on patterns in ocean biology and biogeochemistry over a decade at the BATS site, concentrating on seasonal and interannual changes in community structure, and the physical forcing and other factors controlling the temporal dynamics. Significant seasonal and interannual variability in phytoplankton and bacterioplankton production, biomass, and community structure exists at BATS. There is an absence of a strong relationship between primary production and particle flux at BATS over the entire ten year record. The prokaryotic picoplankton regularly dominate the phytoplankton community, diatom blooms are rare but occur periodically in the BATS time series. The increase in Chl a concentrations during bloom periods are due to increases in most of the taxa present, rather than any single group, and there is seasonal succession of phytoplankton. The bacterioplankton often dominate the living biomass, indicating the potential to consume large amounts of carbon and play a major ecological role within the microbial food web. Bacterial biomass, production, and specific growth rates are highest during the summer. Size structure and composition of the plankton community may be an important factor controlling the quality of dissolved organic matter produced and could affect production of bacterioplankton biomass. Larger heterotrophic plankton play an integral role in the flux of material out of the euphotic zone at BATS. A large number of protozoans are present, which can be a sizable component of sinking flux. Zooplankton contribute significantly to flux via production of rapidly sinking fecal pellets, and vertically migrating zooplankton can actively transport a significant amount of dissolved organic and inorganic carbon and nitrogen to deep water. An important question that remains to be addressed at BATS is how larger climatological events drive some of the interannual variability in the biogeochemistry.