We analyse the way grafted polymers modify the slippage of an entangled polymer melt on an ideal surface. We take into account the deformation of the grafted chains in the flow (non-linear effects) and show that it alters significantly their efficiency as anti-slippers. We calculate the relation between the applied shear stress and the slippage velocity. At low velocities the friction of the underformed grafted chains is strong. Above a certain threshold part of the chain relaxes through monomeric friction, and the stress becomes almost velocity independent. For even higher velocities the contribution of the grafted chains become small and a significant slippage is recovered. More generally, non-linear effects due to deformation of chains in flow are shown to be of importance at most experimental and practical velocities. © 1994.