simulation was tuned to reproduce the measured response. The calorimeter response to a jet was determined by a convolution of the single particle response with the type and mo- mentum distribution of particles constituting a jet as given by a fragmentation model. CDF used QCD dijet events with the pythia fragmentation model to measure the default jet corrections. The pythia fragmentation model agreed well with the particle p$_{T}$ and multi- plicity distributions in a jet measured in p ¯ p data. The herwig event generator was used to crosscheck the pythia fragmentation functions and the results determined using two gener- ators were found to agree well. In this procedure, the difference in calorimeter response to gluon-initiated and quark-initiated jets is automatically included. Although this procedure requires a detailed knowledge of the calorimeter response and a well-tuned simulation, it has the advantages that the correction can be easily determined for any event topology over the entire kinematic range, and real and simulated data have the same corrections and thus can be treated on an equal footing. The inclusive jet cross section measurement [40–45] has been used to test QCD and to search for physics beyond the Standard Model by searching for an excess of events at large p$_{T}$ . During Run I at √$_{s}$ = 1 . 8 TeV, the search was limited by both theoretical and experimental systematic uncertainties even with an integrated luminosity of 100 pb − $^{1}$. The uncertainty on the jet energy scale dominated the experimental uncertainty. NLO pQCD calculations [14– 16] significantly reduced the dependence on the factorization and renormalization scales and the remaining dependence is ∼ 10% and almost independent of jet p$_{T}$ for p$_{T}$ > 100 GeV /c . The jet cross section is not very sensitive to non-perturbative hadronization effects. The underlying event contributes approximately 2 GeV /c of p$_{T}$ to a jet and thus is significant only at low p$_{T}$ . The main theoretical uncertainty arises from uncertainty in the parton distribution functions, especially for large x gluons. Unfortunately, inclusive jet production is the only process in which the high x gluon distribution can be directly measured. The other possible process, photon-jet production, has a limited reach in x and the associated theoretical uncertainties are large. The gluon distributions are also measured from lepton- proton scattering data through QCD scaling violations, but these measurements are also limited to low x values. Because of these limitations, the Run II inclusive jet cross section V. INCLUSIVE JET CROSS SECTION 15