QCD CORRECTED 1/MB CONTRIBUTIONS TO B(B)OVER-BAR-MIXING

We calculate the QCD corrected effective hamiltonian for BBBAR-mixing in heavy quark effective theory including corrections of the order LAMBDA(QCD)/m(b). The matrix elements of the subleading operators arc estimated using the vacuum insertion assumption. We show that the major part of the subleading corrections may be absorbed into the heavy meson decay constant f(B); the remaining corrections are only due to QCD effects and give an enhancement of DELTAM of 5%.