  I give a brief outline of the theoretical framework for the modern treatment
of the strong interaction effects in heavy quark decays, based on first
principles of QCD. This model-independent approach is required to meet the
precision of current and future experiments. Applications to a few problems of
particular practical interest are reviewed, including the precise determination
of V_{cb} and V_{ub}. I emphasize the peculiarities of simultaneously
accounting for the perturbative and power-suppressed effects necessary for
accurate predictions.
