  We analyze the evolution of the perturbations in the inflaton field and
metric following the end of inflation. We present accurate analytic
approximations for the perturbations, showing that the coherent oscillations of
the post-inflationary condensate necessarily break down long before any current
phenomenological constraints require the universe to become radiation
dominated. Further, the breakdown occurs on length-scales equivalent to the
comoving post-inflationary horizon size. This work has implications for both
the inflationary "matching" problem, and the possible generation of a
stochastic gravitational wave background in the post-inflationary universe.
