  We briefly review the theory of gamma ray production in solar flares and
present the highlights of the observations and their implications.
Specifically: (i) the gamma ray data show that a large fraction of the released
flare energy is in accelerated ions, mostly around 1 MeV/nucleon; (ii) the
accelerated He-3, heavy ion, and relativistic electron abundances are enriched,
implying that the particle acceleration is dominated by stochastic gyroresonant
interactions with plasma turbulence; (iii) there is evidence for the
enhancement of the abundances of ambient chromospheric elements with low first
ionization potentials; (iv) the observed Li-7 and Be-7 lines, at 0.429 MeV and
0.478 MeV due to alpha-alpha interactions, show that both the accelerated alpha
particle and the ambient He abundances are significantly enhanced.
