The different types of sediments in the Indian Ocean and their areal distribution are described first. Following this their calcium carbonate content is discussed. The origin of these different deposits depends on the character and amount of the terrigenous detritus, on the nature of the organic substances supplied to the sediment, and on the physical and chemical properties of the ocean water which influence the carbonate content of the deposits. The varied influence of these factors in the individual ocean regions permits the interpretation of the large-scale distribution of the deep-sea sediments and of their carbonate content on the bottom of the Indian Ocean. On the basis of the results of investigations by the "Meteor" Expedition of the sediments of the equatorial A lantic Ocean it is possible to explain the stratigraphic relationships of the pelagic sediments of the Indian Ocean in their major features and to gain some knowledge of its history back to the last glacial period. This knowledge agrees with observations in the equatorial Atlantic Ocean, thus giving a wider regional significance to the conclusions based on the data from the Atlantic Ocean.