  GRS 1915+105 was observed by the CGRO/OSSE 9 times in 1995-2000, and 8 of
those observations were simultaneous with those by RXTE. We present an analysis
of all of the OSSE data and of two RXTE-OSSE spectra with the lowest and
highest X-ray fluxes. The OSSE data show a power-law--like spectrum extending
up to ~600 keV without any break. We interpret this emission as strong evidence
for the presence of non-thermal electrons in the source. The broad-band spectra
cannot be described by either thermal or bulk-motion Comptonization, whereas
they are well described by Comptonization in hybrid thermal/ non-thermal
plasmas.
