The time-integrated B-0(B) over bar(0) mixing parameter and the forward-backward charge asymmetry in the process e(+)e(-) --> b (b) over bar 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(FB)(b) = 0.0960 +/- 0.0066(stat.) +/- 0.0033(sys.), chi(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(FB)(0,b) = 0.1015 +/- 0.0064(stat.) +/- 0.0035(sys.), sin(theta)(2)W<(theta)over bar> = 0.2318 +/- 0.0013. (C) 1999 Published by Elsevier Science B.V. All rights reserved.