  Evaluating the relic density of dark matter is an interesting possibility to
constrain the parameter space of new physics models. However, this calculation
is affected by several sources of uncertainty. On the particle physics side,
considerable progress has been made in the recent years concerning the
calculation of the annihilation cross-section of dark matter, which is needed
in this context. In particular, within the Minimal Supersymmetric Standard
Model, the theoretical uncertainty has been reduced through the calculation of
loop corrections. The present contribution gives an overview over the
achievements that have been made in QCD corrections to neutralino pair
annihilation. The numerical impact is illustrated for a few examples.
