  We present evidence for diffractive exclusive dijet production with an
invariant dijet mass greater than 100 GeV in data collected with the D0
experiment at the Fermilab Tevatron Collider. A discriminant based on
calorimeter information is used to measure a significant number of events with
little energy (typically less than 10 GeV) outside the dijet system, consistent
with the diffractive exclusive dijet production topology. The probability for
these events to be explained by other dijet production processes is $2 \times
10^{-5}$, corresponding to a 4.1 standard deviation significance.
