A total of about 900000 Z0 --> qqBAR decays have been analyzed to meas
ure the B0 - B0BAR mixing probability. Two different b tagging techniq
ues have been used: events with two leptons and events with one lepton
and one LAMBDA. From a combination of the two methods the average mix
ing parameter, chi, was determined to be (12.1 +/- 1.6(stat.) +/- 0.4(
syst.) +/- 0.4(model))%.