  We are interested to the existence of standing waves for the nonlinear Klein
Gordon equation {\epsilon}^2{\box}{\psi} + W'({\psi}) = 0 in a bounded domain
D. The main result of this paper is that, under suitable growth condition on W,
for {\epsilon} sufficiently small, we have at least cat(D) standing wavesfor
the equation ({\dag}), while cat(D) is the Ljusternik-Schnirelmann category.
