  Hard diffraction in events with dijets and rapidity gaps has been studied by
D\O and CDF for three processes: hard color singlet exchange, hard single
diffraction, and hard double pomeron exchange, using Tevatron $\bar pp$ data at
$\sqrt{s}$ = 630 GeV and 1.8 TeV. Measurements of rates, $\eta, E_T$ and
$\sqrt{s}$ dependencies are presented and comparisons made with predictions of
several models.
