  We investigate the global dynamics of the universe within the framework of
the Interacting Dark Matter (IDM) scenario. Considering that the dark matter
obeys the collisional Boltzmann equation, we can obtain analytical solutions of
the global density evolution, which can accommodate an accelerated expansion,
equivalent to either the {\em quintessence} or the standard $\Lambda$ models.
This is possible if there is a disequilibrium between the DM particle creation
and annihilation processes with the former process dominating, which creates an
effective source term with negative pressure. Comparing the predicted Hubble
expansion of one of the IDM models (the simplest) with observational data, we
find that the effective annihilation term is quite small, as suggested by
various experiments.
