The distribution of 3He has been measured on an Australia-Bali transect, across the Pacific-Indian throughflow region of the Eastern Indian Ocean, in SE and NW monsoonal regimes. Additional samples were also collected directly on the main sills over which water is exchanged between the Indonesian Seas and the Indian Ocean. The 3He data show that the South Banda Sea deep waters, between 800 and 1400 m, leave the Banda basin over the sills in the straits of Sumba, Savu, Roti and Timor and enter the equatorial Indian Ocean. The permanence of the 3He in both opposite monsoonal regimes, and the only weak dilution of the 3He signal between the straits and the Australia-Bali section hundreds of kilometers apart, suggest that this deep outflow is not negligible. ¿ 1997 American Geophysical Union