  The lifetime splitting between the B^+ and B_d^0 mesons has recently been
calculated in the next-to-leading order of QCD. These corrections are necessary
for a reliable theoretical prediction, in particular for the meaningful use of
hadronic matrix elements computed with lattice QCD. Using results from quenched
lattice QCD we find tau(B^+)/tau(B^0_d)=1.053 +/- 0.016 +/- 0.017, where the
uncertainties from unquenching and 1/m_b corrections are not included. The
lifetime difference of heavy baryons Xi_b^0 and \Xi_b^- is also discussed.
