  We describe how to compute planar gluon scattering amplitudes at strong
coupling in N=4 super Yang Mills by using the gauge/string duality. The
computation boils down to finding a certain classical string configuration
whose boundary conditions are determined by the gluon momenta. The results are
infrared divergent. We introduce the gravity version of dimensional
regularization to define finite quantities. The leading and subleading IR
divergencies are characterized by two functions of the coupling that we compute
at strong coupling. We compute also the full finite form for the four point
amplitude and we find agreement with a recent ansatz by Bern, Dixon and
Smirnov.
