  We comment on a recent Letter by Braunstein and Buceta [PRL vol.81, 630
(1998)], in which a novel equation has been proposed to describe the dynamics
of interfaces in the presence of quenched disorder. We argue that the ansatz
Braunstein and Buceta presented is just an effective description of the very
short times regime and has no significance for the macroscopic (large scale)
behaviour of the interface. We calculate an expression for the short time
behaviour of the interface that is valid for any q (and not only at q_c).
