We report on our experimental studies of the electrostatic charging properties of an Apollo 17 soil sample and two lunar simulants, Minnesota Lunar Simulant (MLS-1) and Johnson Space Center (JSC-1). We have measured their charge after exposing individual grains to a beam of fast electrons with energies in the range of 20≤E≤90 eV. Our measurements indicate that the secondary electron emission yield of the Apollo 17 sample is intermediate between MLS-1 and JSC-1, closer to that of MLS-1. ¿ 1998 American Geophysical Union