  The observations of microlensing events in the Large Magellanic Cloud suggest
that a sizable fraction (\sim 50%) of the galactic halo is in the form of
MACHOs (Massive Astrophysical Compact Halo Objects) with an average mass $\sim
0.27 M_{\odot}$, assuming a standard spherical halo model. We describe a
scenario in which dark clusters of MACHOs and cold molecular clouds (mainly of
H_2) naturally form in the halo at galactocentric distances larger than 10-20
kpc.
