It is demonstrated that equilibrium concentrations of surface vacancies on the principal planes of metal single crystals may exceed the concentrations of atoms in adsorbed positions. Surface vacancy concentrations on some of the higher index planes of gold are calculated to be of the order of 10−2or more at 1000°K. The interactions of mobile surface vacancies with steps are considered and contrasted with those of atoms diffusing on the surface. The possible influence of surface point defects on transport and growth mechanisms are discussed assuming that vacancy generation occurs mainly at kink sites on the free surface.