Recent observations have extended the spectra of the impulsive phase o
f flares to the GeV range. Such high-energy photons can be produced ei
ther by electron bremsstrahlung or by decay of pions produced by accel
erated protons. In this paper we investigate the effects of processes
which become important at high energies. We examine the effects of syn
chrotron losses during the transport of electrons as they travel from
the acceleration region in the corona to the gamma-ray emission sites
deep in the chromosphere and photosphere, and the effects of scatterin
g and absorption of gamma rays on their way from the photosphere to sp
ace instruments. These results are compared with the spectra from so-c
alled electron-dominated flares, observed by GRS on the Solar Maximum
Mission, which show negligible or no detectable contribution from acce
lerated protons. The spectra of these flares show a distinct steepenin
g at energies below 100 keV and a rapid falloff at energies above 50 M
eV. Following our earlier results based on lower energy gamma-ray flar
e emission we have modeled these spectra. We show that neither the rad
iative transfer effects, which are expected to become important at hig
her energies, nor the transport effects (Coulomb collisions, synchrotr
on losses, or magnetic field convergence) can explain such sharp spect
ral deviations from a simple power law. These spectral deviations from
a power law are therefore attributed to the acceleration process. In
a stochastic acceleration model the low-energy steepening can be attri
buted to Coulomb collision and the rapid high-energy steepening can re
sult from synchrotron losses during the acceleration process.