This project will analyze and interpret previously collected samples of He-3 from the plume of He-3 emanating at hydrothermal sources on the East Pacific Rise. These data along with other samples from the water column and direct measurements of current will be used to determine the circulation at 2-3 km in the eastern Pacific Ocean between about 5 degrees and 20 degrees South latitude. The results will be compared to long-standing ideas about interior circulation in the deep oceans.