  We discuss the emergence of W-algebras as asymptotic symmetries of
higher-spin gauge theories coupled to three-dimensional Einstein gravity with a
negative cosmological constant. We focus on models involving a finite number of
bosonic higher-spin fields, and especially on the example provided by the
coupling of a spin-3 field to gravity. It is described by a SL(3) \times SL(3)
Chern-Simons theory and its asymptotic symmetry algebra is given by two copies
of the classical W_3-algebra with central charge the one computed by Brown and
Henneaux in pure gravity with negative cosmological constant.
