The three-dimensional structure of the Atlantic western boundary currents from 50°S to 10°N is described using the alongshore transports to the west of the WOCE hydrographic line A17, and the velocities across four transverse lines in the major circulation regimes at nominal latitudes 50°S, 35°S, 13°S, and 10°N (Figure 1). Meridionally, the modifications brought on the wind-driven boundary flows of the upper ocean by the thermohaline mode vary from about 20+/-10 Sv southward in the Argentine Basin to about 40+/-10 Sv northward in the northern subequatorial domain, with a vanishing effect around 33°S. The limits of the major boundary currents (Brazil Current, North Brazil Undercurrent, Deep Western Boundary Current) are obtained in 9 density layers representative of the water mass structure. Laterally, boundary flows of 100 km -200 km width are observed in the upper ocean (~300 km in the Falkland Current), extending farther seaward at depth. Intense return flows adjacent to the boundary currents are observed at 50°S (The Falkland Return Current), near 35°S, and at 6°N-10°N, the latter being probably highly variable.