Enhancements in the fluxes of relativistic electrons trapped within the Earth's magnetosphere have been measured by the high-energy particle spectrometer, part of the particle environment monitor on the upper atmosphere research satellite (UARS). The largest increase in the electron fluxes with energies greater than 1 MeV observed on UARS from October 1991 through July 1994 was in early May 1992. The fluxes of trapped electrons in the drift loss cone and locally precipitating electrons showed differing buildup and decay rates as a function of invariant latitude. Increases of more than 2 orders of magnitude were observed in drift loss cone fluxes at magnetic latitudes of 40¿--66¿ and in precipitating fluxes from 48¿ to 66¿. The energy flux contained in the most intense local precipitation observed was ~0.1 erg cm-2 s-1, entering the atmosphere and creating up to 1000 ion pairs cm-3 s-1 at 55-km altitude. The daily averaged energy flux from directly precipitating electrons with energies >1 MeV deposited >1020 erg d-1 worldwide into the atmosphere for the period May 12--21, 1992, producing >1031 odd nitrogen molecules below 60-km altitude. ¿ American Geophysical Union 1995