During 1978 and 1979, four experiments with clusters of 6 to 10 drifting buoys were carried out in the Atlantic Equatorial Undercurrent. The measurements where intended to estimate horizontal mixing and its possible contribution to the salt loss of the high-salinity core related to the Equatorial Undercurrent. The buoys were drogued at the estimated depth of the salinity core of 70 m to 90 m. The diameters of the spreading clusters ranged from 3 to 10 km. Each experiment was maintained for about 2 days. During this period the buoys were tracked by radar from a nearby operating research vessel. From the observed tracks, horizontal turbulent mixing coefficients were deduced. The results show a dependence on the horizontal scale of l1.43. This is not significantly different from an expected l4/3 law. Using the obtained scale dependence, the observatiions are extrapolated to the scale of the salinity core of 150 km obtained from hydrographic observations, resulting in a turbulent mixing coefficients of 6.5¿106 cm2 s-1. Combining these numbers with the horizontal gradients of the salinity core, one obtains a salt loss of 1.42 g s-1 cm-1, which amounts to 20% of the complete salt loss of 7.2 g s-1 cm-1 compiled by Katz et al. (1980).