  Nonperturbative corrections up to $m_b^{-2}$ to the heavy lepton energy
distributions are investigated in the inclusive semileptonic weak decays of
heavy flavors in QCD. In the case of $B$-meson decays, for $b \ra u\tau\bnu$
transitions they decrease the decay rate by 6\% of its perturbative value,
while for $b \ra c\tau\bnu$ they decrease it by 10\%.
