Simultaneous observations of energetic ions (>50 keV) and electrons (>220 keV) by the IMP-7 and IMP-8 spacecraft carrying identical instruments and located within the distant (~37 Re) magnetotail and upstream of the bow shock, respectively, are reported during the period 0000-1100 UT on October 31, 1977. During this period, ISEE-1 detectors had detected an upstream ion event [Ipavich et al., 1979>. The IMP observations, including measurements of the interplanetary magnetic field (IMF), reveal the following: (1) energetic ions and electrons were present inside the plasma sheet >1 hour prior to onset of the event upstream at IMP-8. (2) Ion (50≤E≲200 keV) intensities inside the plasma sheet were always higher than those upstream by factors of ~2 to ~8. (3) The ion energy spectrum upstream of the shock can be fit well by a power law, dj/dE∝E-4.1, from ~50 keV to ~2 MeV; observations at higher energies were precluded by high fluxes of ambient solar energetic particles. (4) Dawn-dusk anisotropies of upstream ions as large as 5:1 are interpreted as due to density gradients; anisotropies in the plasma sheet were, at times, both earthward and tailward. (5) The presence of ions upstream was controlled by the direction of the IMF: connection to the bow shock was necessary, but not sufficient, for the appearance of ions. These observations show that ions observed upstream of the shock on October 31, 1978, most likely originated from within the earth's plasma sheet; a phenomenological model is suggested for such particle ''leakage.'' The observations are inconsistent with most major predictions of the Fermi acceleration model for such events, including the energy extent, the shape of the ion spectrum, the particle anisotropies, and the IMF connection time.