A measurement of the forward-backward asymmetry (A(FB)) of Drell-Yan lepton pairs in pp collisions at root s = 7 TeV is presented. The data sample, collected with the CMS detector, corresponds to an integrated luminosity of 5 fb(-1). The asymmetry is measured as a function of dilepton mass and rapidity in the dielectron and dimuon channels. Combined results from the two channels are presented, and are compared with the standard model predictions. The A(FB) measurement in the dimuon channel and the combination of the two channels are the first such results obtained at a hadron collider. The measured asymmetries are consistent with the standard model predictions. (c) 2012 CERN. Published by Elsevier B.V. All rights reserved.