Electron and ion current measurements made by the Langmuir probe on the Pioneer Venus Orbiter exhibit significant enhancements just upstream from the Venus bow shock where one might have expected only solar wind plasma to be present. The region of enhancement, which we call the Venus precursor, is approximately centered on the subsolar point but extends in latitude up to solar zenith angles of about 80¿; i.e., ahead of nearly the entire dayside shock. At higher latitudes, where its radial profile can be measured, the precursor extends about 1000 km ahead of the shock. The electron current is enhanced by a factor of about 1.6 at the nose, while the net ion current is enhanced by only a few percent because it is dominated by a large, but fixed, photoelectron emission current. There is little change in the amplitude and latitude of the precursor from orbit to orbit, a stability that suggests that this phenomenon is not very sensitive to the often variable solar wind and interplanetary magnetic field conditions. We suspect that the precursor signatures represent the effects of a small population of energetic ions in this region. Several possible planetary sources for these ions are discussed. ¿ American Geophysical Union 1988