From earth-based Doppler and interferometric radio observations we determined the paths, in three dimensions and as functions of time, taken by the Pioneer probes as they fell to the surface of Venus. From the motion of each probe below about 65-km altitude we were able to infer the ambient wind velocity with an estimated uncertainty of about 1 m s-1 in each vector component. The magnitude of the velocity was about 1 m s-1 or less near the surface of the planet and about 100 m s-1 near 65-km altitude at all four probe locations. Distinct strata of high wind shear were centered at altitudes of 15, 45, and 60 km, where the atmosphere is most stable against verticle motion. Except within a few kilometers of the surface, the wind velocity was always directed within a few degrees of due west. At the day and the night probe sites, which were separated by 100¿ in longitude and 3¿ in latitude, the altitude profiles of the westward velocity were virtually identical. Thus the dominant motion of the lower atmosphere seems to be a retrograde zonal rotation. Eddies appear to account for most of the instantaneous meridional velocity. However, in the radiatively heated middle cloud layer, between 50- and 55-km altitude, equatorward flow of 1--7 m s-1 was observed for all four probes. These observations, coupled with other observations of ~10 m s-1 poleward average meridinal velocity for cloud top features at about 65-km altitude, suggest that within the clouds a thermally driven mean meridional circulation is superimposed on the much more rapid zonal rotation.