The measurements of Rb=σ(e+e-→bb)/ σ(e+e-→qq) and of the b quark forward–backward charge asymmetry, Afbb, at centre-of-mass energies above the Z pole are described. The measurement of Rb is performed at √s between 130 and 189 GeV using a b-tagging method that exploits the relatively large decay length of b-hadrons. The measurement of Afbb is performed using the large statistics event sample collected at √s=189 GeV with a lepton-tag analysis based on the selection of prompt muons and electrons. The results at at √s=189 GeV are Rb=0.163±0.013(stat.)±0.005(syst.), A b/fb=0.61±0.18(stat.)±0.09(syst.).