The time-integrated B 0 B ̄ 0 mixing parameter and the forward-backward charge asymmetry in the process e + e − →b b ̄ are measured in hadronic Z events containing prompt muons or electrons, collected by the L3 experiment in the years 1990 to 1995. The total sample of 3.3 milion hadronic Z events with a mean centre-of-mass energy of 91.26 GeV yields: A b FB =0.0960±0.0066( stat .)±0.0033( sys .), χ b =0.1192±0.0068( stat .)±0.0051( sys .). This asymmetry measurement together with measurements at energies away from the Z pole energy yield a pole asymmetry and corresponding effective electroweak mixing angle of: A 0,b FB =0.1015±0.0064( stat .)±0.0035( sys .), sin 2 θ ̄ W =0.2318±0.0013 .