The areal distribution of calcium carbonate in the surface sediments of the Atlantic Ocean and adjacent seas and oceans is mapped on the basis of over 1700 data points. The first-order relation of carbonate distribution to water depth is evident in both the areal distribution and the plots of carbonate versus depth for 11 areas of the Atlantic. Superimposed on this relation are significant variations in both the 100% and the 0% CaCO3 depth intercepts, analogous to the (calcite) lysocline and the (calcite) carbonate compensation depth, respectively. Variations in these critical parameters between the 11 areas are related to the three rate processes which control carbonate distributions: surface productivity, dissolution, and dilution by noncarbonate biogenic and nonbiogenic sediment. The areal distribution of carbonate in surface sediments is compared with that in sediments deposited at the end of the last glacial epoch, 18,000 yr B.P., when carbonate abundance was markedly lower.