The dijet invariant mass distribution has been measured in the region between 140 and 1000 GeV/${\mathit{c}}^{2}$, in 1.8 TeV p p\ifmmode\bar\else\textasciimacron\fi{} collisions. Data collected with the Collider Detector at Fermilab show agreement with QCD calculations. A limit on quark compositeness of ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{c}}$>1.3 TeV is obtained. Axigluons with masses between 240 and 640 GeV/${\mathit{c}}^{2}$ are excluded at 95% C.L. if we assume ten open decay channels. Model-independent limits on the production of heavy particles decaying into two jets are also presented.