  Events in PbarP collisions at sqrt(s)=1.8 TeV with total transverse energy
exceeding 500 GeV are used to set limits on quark substructure. The data are
consistent with next-to-leading order QCD calculations. We set a lower limit of
2.0 TeV at 95% confidence on the energy scale Lambda_LL for compositeness in
quarks, assuming a model with a left-left isoscalar contact interaction term.
The limits on Lambda_LL are found to be insensitive to the sign of the
interference term in the Lagrangian.
