Precision determination of the Cabibbo-Kobayashi-Maskawa element V(cb).

We extract the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element V(c)} and the most relevant parameters of the heavy quark expansion from data of inclusive semileptonic B decays. Our calculation includes the recently computed O(α(s)Λ(QCD)(2)/m(b)(2)) corrections and a careful estimate of the residual theoretical uncertainty. Using a recent determination of the charm quark mass, we obtain |V(cb)|=(42.21±0.78)×10(-3) and m(b)(kin)(1  GeV)=(4.553±0.020)  GeV.