Résumé : The tt- production cross section (σtt-) is measured in proton-proton collisions at √s = 7TeV in data collected by the CMS experiment, corresponding to an integrated luminosity of 2.3 fb-1. The measurement is performed in events with two leptons (electrons or muons) in the final state, at least two jets identified as jets originating from b quarks, and the presence of an imbalance in transverse momentum. The measured value of σtt- for a top-quark mass of 172.5 GeV is 161:9 ± 2:5 (stat.) +5:1 -5:0 (syst.) ± 3:6 (lumi.) pb, consistent with the prediction of the standard model. © SISSA 2012.