  The possibility that the present acceleration of the universe is driven by a
kind of viscous fluid is exploited. At background level this model is similar
to the generalized Chaplygin gas model (GCGM). But, at perturbative level, the
viscous fluid exhibits interesting properties. In particular the oscillations
in the power spectrum that plagues the GCGM are not present. Possible
fundamental descriptions for this viscous dark energy are discussed.
