Two deep CTD sections were occupied by U.S.N.S. Wilkes in the Central Indian Basin during April 1979, one across the basin along Lat. 12S, and the other from Lat. 12S to 1N along Longs. 88-89E. These observations, in combination with other (mostly recent) data, demonstrate a two-layer structure in the deep water of the basin. The upper deep water (2000-3800 m) is supplied from a mid-depth western-boundary current flowing directly northward from the Antarctic along the eastern flank of the Central Indian Ridge....