  The role of global QCD analysis of parton distribution functions (PDFs) in
collider physics at the Tevatron and LHC is surveyed. Current status of PDF
analyses are reviewed, emphasizing the uncertainties and the open issues. The
stability of NLO QCD global analysis and its prediction on "standard candle"
W/Z cross sections at hadron colliders are investigated. The importance of the
precise measurement of various W/Z cross sections at the Tevatron in advancing
our knowledge of PDFs, hence in enhancing the capabilities of making
significant progress in W mass and top quark parameter measurements, as well as
the discovery potentials of Higgs and New Physics at the Tevatron and LHC, is
emphasized.
