  We present an analytical derivation of the excess current in Josephson
junctions within the Octavio-Tinkham-Blonder-Klapwijk theory for both symmetric
and asymmetric barrier strengths. We confirm the result found numerically by
Flensberg et al. for equal barriers [Phys. Rev. B 38, 8707 (1988)], including
the prediction of negative excess current for low transparencies, and we
generalize it for differing barriers. Our analytical formulae provide for
convenient fitting of experimental data, also in the less studied, but
practically relevant case of the barrier asymmetry.
