  The naive implementation of finite width effects in processes involving
unstable particles can violate gauge invariance. For the example of radiative
$W$ production and decay, $q\bar q' \to \ell\nu\gamma$, at tree level, it is
demonstrated how gauge invariance is restored by including the imaginary part
of triangle graphs in addition to resumming the imaginary contributions to the
$W$ vacuum polarization. Monte Carlo results are presented for the Fermilab
Tevatron.
