The Atlantic Geosecs data for main oceanic thermocline provide a basis for reexamining the conventional views with regard to the origin and movement of these waters. Our analysis of these data suggests the following: (1) More attention must be given the dynamics associated with the fronts at 15¿N and 15¿S. The study of these important features has been sorely neglected. (2) The possibility that waters in the equatorial thermocline are generated by vertical mixing rather than by lateral ventilation must be seriously considered. (3) The tritium results in hand clearly demonstrate the potential of repeated surveys of this transient tracer in refining our knowledge of thermocline dynamics. (4) the tritium results are not, however, likely to resolve the question of the relative importance of vertical and horizontal mixing. This can only be done through the direct addition of tracers to the interior of the thermocline.