  The subject of particle-antiparticle mixing in the neutral B meson systems is
reviewed. The formalism of B0-B0bar mixing and basic Standard Model predictions
are given, before experimental issues are discussed and the latest combinations
of experimental results on mixing parameters are presented, including those on
mixing-induced CP violation, mass differences, and decay-width differences.
Finally, time-integrated mixing results are used to improve our knowledge on
the fractions of the various b-hadron species produced at high energy
colliders.
