  Jet production at the Tevatron probes some of the smallest distance scales
currently accessible. A gluon distribution that is enhanced at large x compared
to previous determinations provides a better description of the Run 1b jet data
from both CDF and D0. However, considerable uncertainty still remains regarding
the gluon distribution at high x. In this paper, we examine the effects of this
uncertainty, and of the remaining uncertainties in the NLO QCD theory, on jet
cross section comparisons to Run 1b data. We also calculate the range of
contributions still possible from any new physics. Predictions are also made
for the expanded kinematic range expected for the ongoing Run 2 at the Tevatron
and for the LHC.
