Two types of the U-series disequilibrium methods are available for dating different ocean formations and are based on radioactive (1) decay or (2) accumulation of daughter isotope. At the present time the most widespread and well-founded methods are (1) 230Thexcess, 231Paexcess, and (2) 230Th/234U and 231Pa/235U dating methods of different ocean formations. A number of ocean objects is suitable for 230Thxs and 231Paxs dating: deep-sea sediments of different origin such as carbonate (foraminiferal), silicate (radiolarian) or metalliferous sediments, and ferromanganese nodules and crusts. Both the 230Th/U and 231Pa/U methods play an important role in dating corals and mollusk shells, as well as the 230Th/U method which is most widely applied in dating seafloor massive sulfide deposits in the ocean hydrothermal zones. Modern mass spectrometric analysis allows to determine 230Thxs and 230Th/U ages between several decades to ca. 500 kyr, and 231Paxs and 231Pa/U ages up to ca. 250 kyr. Mass spectrometric measureme