The effect of all possible parton subprocesses on the normalization of the Drell‐Yan cross section d&sgr;/dQ2is investigated. The relation with deep‐inelastic scattering is discussed, and we show how the results, and in particular the quark‐quark correction, can be converted to the MS‐scheme. The effect of all contributions on the proton‐proton cross section is calculated from deep‐inelastic scattering data, using second order QCD, with matching conventions. We consider the full order‐&agr;scorrections, the second order qq correction and make an estimate of the gluon‐gluon contribution.