  We calculate the three-point correlation function evaluated at horizon
crossing for a set of interacting scalar fields coupled to gravity during
inflation. This provides the initial condition for the three-point function of
the curvature perturbation in the Sasaki--Stewart \delta N formulation. We find
that the effect is small, of the order of a slow-roll parameter, and that the
non-gaussianity can be determined on large scales once the unperturbed
background evolution is known. As an example of the use of our formalism, we
calculate the primordial non-gaussianity arising in a model of assisted
inflation.
