  We study the Regge and hard scattering limits of the one-loop amplitude for
massless open string states in the type I theory. For hard scattering we find
the exact coefficient multiplying the known exponential falloff in terms of the
scattering angle, without relying on a saddle point approximation for the
integration over the cross ratio. This bypasses the issues of estimating the
contributions from flat directions, as well as those that arise from
fluctuations of the gaussian integration about a saddle point. This result
allows for a straightforward computation of the small- angle behavior of the
hard scattering regime and we find complete agreement with the Regge limit at
high momentum transfer, as expected.
