  The role of dark matter halos in galaxy disk evolution is reviewed, in
particular the stabilisation of disks through self-gravity reduction, or the
bar development through angular momentum exchange. Triaxial dark halos tend to
weaken bars. When the dark mass inside the bar region is negligible, the bar
develops through angular momentum exchange between inner and outer disk, and
between stars and gas. Self-regulating cycles on the bar strength may develop
in the presence of external gas accretion. Dynamical friction on dark halos
slows down bars, which puts constraints on the dark matter amount inside the
inner disk. During galaxy formation, baryons can lose most of their angular
momentum if the infall is misaligned with the dark matter axes. Stable disks
can form aligned with the minor axis of the dark halo.
  A sudden change in the infall direction, otherwise steady, can produce the
peculiar polar ring galaxies. The dark matter halo can then be aligned along
the polar disk. Misaligned infall can also maintain lopsidedness, which is only
rarely due to galaxy interactions and mergers.
