It is demonstrated that electric fields applied across phosphor layers strongly influence the cathodoluminescence emitted from these materials at low electron beam energies. The magnitude of these effects suggest that the primary mechanism may be alteration of the relative capture rates of electrons and holes at surface or near-surface defect sites associated with nonradiative energy losses. The sign of these effects in the two materials investigated suggests that the rate limiting step at low electric fields is the capture of electrons. Strong evidence for field-induced polarization and trapping of the beam-created electron-hole pair population is also presented. ©1998 American Institute of Physics.