The South Equatorial Undercurrent (SEUC) in the western to central tropical Atlantic is investigated by a combination of shallow floats, with a few acoustically tracked, shipboard current measurements and hydrography. Float trajectories show a well confined SEUC revealing large standing meanders near its western origin. Transports determined from 31 sections across the SEUC increase from 5.6 Sv at 35°W near the western boundary to 10.2 Sv 800 km farther east. Internal recirculations north and south of the SEUC were indicated by the float trajectories and a weak transport reduction farther along its eastward progression is observed. The deep part of the South Equatorial Current carries on both sides of the SEUC interior water masses westward, and supplies almost 5 Sv to the SEUC between 35°W and 28°W, or about half of the SEUC transport in the interior tropical Atlantic. Copyright 2008 by the American Geophysical Union.