  The J/$\psi$ azimuthal distribution relative to the reaction plane has been
measured by the NA50 experiment in Pb-Pb collisions at 158 GeV/nucleon. Various
physical mechanisms related to charmonium dissociation in the medium created in
the heavy ion collision are expected to introduce an anisotropy in the
azimuthal distribution of the observed J/$\psi$ mesons at SPS energies. Hence,
the measurement of J/$\psi$ elliptic anisotropy, quantified by the Fourier
coefficient v$_2$ of the J/$\psi$ azimuthal distribution relative to the
reaction plane, is an important tool to constrain theoretical models aimed at
explaining the anomalous J/$\psi$ suppression observed in Pb-Pb collisions. We
present the measured J/$\psi$ yields in different bins of azimuthal angle
relative to the reaction plane, as well as the resulting values of the Fourier
coefficient v$_{2}$ as a function of the collision centrality and of the
J/$\psi$ transverse momentum. The reaction plane has been estimated from the
azimuthal distribution of the neutral transverse energy detected in an
electromagnetic calorimeter. The analysis has been performed on a data sample
of about 100 000 events, distributed in five centrality or p$_{\rm T}$
sub-samples. The extracted v$_{2}$ values are significantly larger than zero
for non-central collisions and are seen to increase with p$_{\rm T}$.
