  The coupling $g_{B^\ast B \pi}$ is related to the form factor at zero
momentum of the axial current between $B^\ast$ and $B$ states. Moreover it is
related to the effective coupling between heavy mesons and pions that appear
the heavy meson chiral Lagrangian. This coupling has been evaluated on the
lattice using static heavy quarks and light quark propagators determined by a
stochastic inversion of the fermionic bilinear. We found the value
$g=0.42(4)(8)$. Beside its theoretical interest, this quantity has
phenomenological implications in $B \to \pi + \bar l l$ decays.
