The present experiment was conducted to investigate whether edge and screw dislocations play differentroles in the surface work-hardening of metals deformed in tension. The sides of the crystals were so orientedthat one pair of sides was parallel to the Burgers vector of the dislocations of the primary slip system. Thecrystals were deformed in tension to 0.5% and then unloaded. Subsequently, some crystals were masked onone pair of sides, and others were masked on the other pair of sides. They were then electropolished to removethe surface layers from the unmasked faces. This operation was repeated at several strains. At small strains,edge and screw dislocations play different roles in the surface work-hardening mechanism. However, atlarger strains, both edge and screw dislocations harden the surface equally, and preferential surface work-hardeningincreases as the stress level increases.