Deep-drogued drifters are in use to measure the near-surface geostrophic currents. An attempt is made to study the slippage of these drifters due to wind and Ekman currents. The results are based on a data set from the unstratified North Sea obtained in winter 1991--1992, where the currents were decomposed into Ekman currents and barotropic currents. The influence of these Ekman currents on the drift performance of drifters drogued below the mixed layer in the barotropic current is determined by using quadratic drag laws. In 90% of all cases (1540 data points) the combined effect of wind drag and Ekman currents on buoy and 100 m tether produces a slippage of less than 2 cm/s. Drifters drogued within the mixed layer show less slippage due to the reduced drag on the tether, but they are primarily designed to measure the actual near-surface currents, which are strongly dependent on the wind conditions. It is concluded that deep-drogued drifters are a reliable device to study weakly baroclinic geostrophic currents. ¿ American Geophysical Union 1996