  We show that the distribution of the conductance in quasi-one-dimensional
systems with surface disorder is correctly described by the
Dorokhov-Mello-Pereyra-Kumar equation if one includes direct processes in the
scattering matrix S through Poisson's kernel. Although our formulation is valid
for any arbitrary number of channels, we present explicit calculations in the
one channel case. Ours result is compared with solutions of the Schroedinger
equation for waveguides with surface disorder calculated numerically using the
R-matrix method.
