This volume comprises the final report of the research project entitled the Dynamics of the Deep Ocean Circulation. The layered structure of the subsurface circulation, which had been predicted in the hypothetical model proposed prior to the research, is verified through Eulerian and Lagrangian measurements of current. By the use of the numerical model, the deep circulation of the Philippine Sea, which has been long supposed to be isolated from the North Pacific, is revealed to be derived in close association with that of the latter ocean. Behavior of the deep current around the equator is also clarified by numerical modeling. By the extensive use of sediment trapping technology, it becomes clear that sinking sediments play an important role in the distribution of chemical substances in the deep ocean. Graduate students in the field of oceanography will find this a good textbook.