  We review recent advances in the theory of strong-interaction effects and
final-state interactions in hadronic weak decays of heavy mesons. In the
heavy-quark limit, the amplitudes for most nonleptonic, two-body B decays can
be calculated from first principles and expressed in terms of semileptonic form
factors and light-cone distribution amplitudes. We summarize the main features
of this novel QCD factorization and discuss its phenomenological applications
to B->D^(*)+L decays (with L a light meson), and to the rare charmless decays
B->pi+K and B->pi+pi.
