We have used 106 pb(-1) of data collected in <p(p)over bar> collisions
at root s = 1.8 TeV by the Collider Detector at Fermilab to measure j
et angular distributions in events with two jets in the final state. T
he angular distributions agree with next to leading order predictions
of QCD in all dijet invariant mass regions. The data exclude at 95% CL
a model of quark substructure in which only up and down quarks are co
mposite and the contact interaction scale is Lambda(ud)(+) less than o
r equal to 1.6 TeV or Lambda(ud)(-) less than or equal to 1.4 TeV. For
a model in which air quarks are composite the excluded regions are La
mbda(+) less than or equal to 1.8 TeV and Lambda(-) less than or equal
to 1.6 TeV.