  I report on recent developments in the heavy-quark effective theory and its
application to $B$ meson decays. The parameters of the effective theory, the
spin-flavor symmetry limit, and the leading symmetry-breaking corrections to it
are discussed. The results of a QCD sum rule analysis of the universal
Isgur-Wise functions that appear at leading and subleading order in the $1/m_Q$
expansion are presented. I illustrate the phenomenological applications of this
formalism by focusing on two specific examples: the determination of $V_{cb}$
from the endpoint spectrum in semileptonic decays, and the study of
spin-symmetry violating effects in ratios of form factors. I also briefly
comment on nonleptonic decays.
