  We derive the lepton spectrum in semileptonic beauty decays from a
nonperturbative treatment of QCD; it is based on an expansion in $1/m_Q$ with
$m_Q$ being the heavy flavour quark mass. The leading corrections arising on
the $1/m_Q$ level are completely expressed in terms of the difference in the
mass of the heavy hadron and the quark. Nontrivial effects appear in $1/m_Q^2$
terms affecting mainly the endpoint region; they are different for meson and
baryon decays as well as for beauty and charm decays.
