This chapter discusses production of atomic defects in pure, single crystalline metals. The onset energies of damage production for irradiation along some of the main crystal directions is lower than the displacement energy along this lattice direction. This is due to defect production along lattice directions off the irradiation direction, if these directions have sufficiently low displacement energies. These energies are derived from transmission electron microscopy (TEM) observation of dislocation loops. Analysis of the directional dependence of defect production in single crystals allows to determine the anisotropy of the displacement energy. The most simple analysis for cubic metals employs an expansion of Td(θ, φ) in cubic harmonics with the displacement energies along the three main crystal directions as parameters. When resistivity damage rates are fitted, the resistivity contribution per unit concentration of Frenkel pairs ρF, can be derived. A more detailed displacement energy profile is obtained by assigning "windows" of certain size and shape, with low displacement energies to the low index directions. When a sufficient amount of data is available, a finer subdivision of the displacement energy map is possible for aluminum (Al), copper (Cu) and platinum (Pt). Recovery experiments on single crystals allow to assign various lattice directions (or “windows”) to the production of a certain defect, characterized by its annealing stage or temperature.