Nickel (110) surfaces, in clean and nearly clean conditions, have been studied by low‐energy electron diffraction. When free from foreign atoms, the surface (110) plane of atoms has the normal arrangement expected for such a plane. Very slight contamination by oxygen (and perhaps other atoms) results, in some cases, in an arrangement of the topmost layer of atoms in which nickel and oxygen (or another atom) alternate along each [100] line and also along each [110] line. Study of such a surface has shown that the superficial half‐layer of nickel atoms is displaced toward the bulk of the crystal by about 0.10 A.