  We study all tree-level neutralino annihilation processes concerning
energy-dependence at the mSUGRA benchmark point SPS1a using tree-level
calculators MadGraph and CompHEP as well as FormCalc. We further investigate
the total tree-level neutralino annihilation cross section by scanning over the
mSUGRA parameters and identifying the dominant channels in every region. The
results for the cross sections are presented in the m1/2-m0 planes for
different values of tan(beta) and A0. We identify as well the resonances due to
the exchange of the heavy Higgs bosons A and H in the s-channel of many
neutralino annihilation processes, where the total cross section increases
significantly if these Higgs bosons can be produced close to on-shell. Finally,
we provide a few comments on the neutralino annihilation processes at
loop-level.
