We report on a measurement of the ratio of the differential cross sections for Wand Zboson production as a function of transverse momentum in proton–antiproton collisions at s=1.8 TeV. This measurement uses data recorded by the DØ detector at the Fermilab Tevatron in 1994–1995. It represents the first investigation of a proposal that ratios between Wand Zobservables can be calculated reliably using perturbative QCD, even when the individual observables are not. Using the ratio of differential cross sections reduces both experimental and theoretical uncertainties, and can therefore provide smaller overall uncertainties in the measured mass and width of the Wboson than current methods used at hadron colliders.