  We present recent results for the prediction of the Bs lifetime difference
from lattice Heavy Quark Effective Theory simulations. In order to get a
next-to-leading order result we have calculated the matching between QCD and
HQET and the two loop anomalous dimension in the HQET for all the \Delta B=2
operators, in particular for the operators which enter in the width difference.
We obtain for the Bs lifetime difference, (\Delta\Gamma_Bs/\Gamma_Bs)=(5.1+/-
1.9+/- 1.7)10^(-2).
