GLAMAP 2000 presents new reconstructions of the Atlantic's sea surface temperatures (SST) at the Last Glacial Maximum (LGM), defined at both 21,500–18,000 years B.P. (“Last Isotope Maximum”) and 23,000–19,000 years B.P. (maximum glacial sea level low stand and orbital minimum of solar insolation; EPILOG working group; see Mix et al. ). These reconstructions use 275 sediment cores between the North Pole and 60°S with carefully defined chronostratigraphies. Four categories of core quality are distinguished. More than 100 core sections provide a glacial record with subcentennial- to multicentennial-scale resolution. SST estimates are based on a new set of almost 1000 reference samples of modern planktic foraminifera and on improved transfer-function techniques to deduce SST from census counts of microfossils, including radiolarians and diatoms. New proxies also serve to deduce sea ice boundaries. The GLAMAP 2000 SST patterns differ significantly in crucial regions from the CLIMAP  reconstruction and thus are important in providing updated boundary conditions to initiate and validate computational models for climate prediction.