The measurement of current transport due to ballistic, quasimonoenergetic, hot electrons injected into thin layers of GaAs indicates that some electrons transfer into the first satellite valleys (L valleys). Applying hydrostatic pressure, which changes the relative energies of the valleys, results in a corresponding shift of the electron energy for which transfer is evident. Transfer of 25% at atmospheric pressure was estimated for a transit time of 0.03 ps. We have also measured the conduction-band discontinuity between GaAs and AlGaAs and find it to be insensitive to hydrostatic pressure. © 1986 The American Physical Society.