Filamentation has been examined in laser‐produced plasmas in which magnetic fields are present, using a two‐fluid model of the plasma. Configurations in which the low‐frequency perturbation is in turn parallel and perpendicular to the magnetic field have been considered and the instability examined in the two cases. In the latter it is shown that the instability is quenched by large enough fields, while for the ion‐acoustic perturbation the behavior is more complex.