  In the framework of the Potential Theory we prove existence and uniqueness
for the Perron-Wiener-Brelot solution to the Dirichlet problem related to a
family of totally degenerate, in the sense of Bony, differential operators. We
also state and prove a Wiener-type criterium and an exterior cone condition for
boundary regularity.
  Our results apply to a wide family of strongly degenerate operators that
includes the following example~$\l = t^2\Delta_x + \langle x, \nabla_y \rangle
-\partial_t$, for~$(x,y,t) \in \R^N \times \R^{N} \times \R$.
